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[OC] Real-life mileage comparison between hybrid and petrol car

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1.9k points · 6 months ago

Worth noting that if that trend continues into the negative, around -175f, your hybrid's mprg goes negative, and if you drive in reverse your car will actually fill up with gasoline.

/i think that's how it works.


118 points · 6 months ago

This Reddit user is disrupting a $200M industry

The hybrid-related clickbait industry?

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Original Poster183 points · 6 months ago

I'm not sure if that's the case, but I'm willing to try!

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57 points · 6 months ago

I'm sure there's a statistical rule against breaking physics.

Moreso there are rules regarding extrapolating outside the range if data collected. Specifically the prediction intervals at points far outside the collection range become very large

Edit: the dotted line here gets much larger as the dependant variable moves away from its measured mean(average)

3 points · 6 months ago

I think it was a joke...

Either way, it's never a bad time to learn something new!

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You are now a moderator of r/shittyaskscience.

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951 points · 6 months ago

My Prius definitely takes a pretty big MPG hit in the winter time. I have about a 12-15 minute to commute to work. In the summer I average about 45-48mpg. Come winter I'm averaging about 37-39.

328 points · 6 months ago

Yeah the heaters really kill hybrids in my experience. Some days I get as low as 20 in my C-Max Energi. 10 minute commute to work, the temperature gets up enough to run the heater probably 6 minutes in.

It's also telling that internal combustion cars are always wasting that much energy as waste heat that has to get dumped overboard.

It’s actually closer to 65% or above for most engines. Gasoline engines are around 30/35% efficient. 30% is outputted in the drive shaft, 30% lost to heat in the radiator, 30% lost to heat out of the exhaust, and 10% heat emitted from the block.

280 points · 6 months ago

Didn’t realize I was wasting so much energy. I’m going to go remove my radiator and exhaust. How unnecessary.

68 points · 6 months ago(6 children)
12 points · 6 months ago(0 children)

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23 points · 6 months ago

Probably best to just get rid of the whole car

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28 points · 6 months ago · edited 6 months ago

The Mercedes F1 team has recently achieved more than 50% thermal efficiency, which I think is pretty neat.

That numbers rather misleading as they roll the hybrid system into it. Even at f1 levels of turbo charging and mechanical tolerancing i doubt they have a 50% efficient otto cycle engine. Remember f1 isnt hcci or anyting like that.

A bit like Mitsubishi saying their phev SUV does 300mpg. Its..... Not bullshit, but its not true either.

They are 50% efficient at turning the available energy in the fuel into forward thrust, including the hybrid system and everything that comes with it.

4 points · 6 months ago · edited 6 months ago

It runs at full throttle (and zero throttle) all the time though. Easier to optimize for compared to normal cars that run at varying amounts of throttle.

Also efficiency != mpg

6 points · 6 months ago

That's fine, but the conversation at hand is about ICE thermal efficiency

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Also, the defroster automatically turns on the air conditioner in a lot of cars. A/C dries the air and makes defrosting work better, but the compressor gives you a fairly significant mileage drop.

I find the A/C isn't that bad for the milage the compressor is electric i run the A/C all the time in the summer and i get in the 40 mpg range in the city. Now in the winter my motor and battery has to warm up before the hybrid system kicks in under 20 degrees takes about 45 minutes. Then with the heater on the engine has to turn on much more to keep the water temperature up for heat. Electric and mechanical water pump. My average mpg winter about 30 mpg city don't forget about driving in snow which kills the mpg. Every time i stop i turn the heat off trying to keep engine temp up so the engine is not always cycling on. I would like to see a heat pump system for heat i think it would be a lot more efficient then just hot water. The car is a 2012 Hyundai Sonata the cooling system is very efficient i have seen the engine temp drop down in 90 degree days and the hood is always cool too the touch.

The bigger the temperature difference between inside and outside the less efficient heat pumps are. Long ago they had some heaters that just burned gas for warmth and didn't need a warm engine. The selling point was instant heat but it might also save gas with hybrids in cold places.

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The heaters are just engine heat, it doesn't take any extra energy to heat cabin air. Although the Prius has a 1 kW electric heater to help get the air feeling warm while the internal combustion engine gets up to temperature, that's a drop in the bucket for both heating and energy loss.

The reason you get such terrible mileage is because internal combustion engines and batteries are both inefficient until they reach operating temperature, which takes longer for the engine in the cold.

If you installed a block heater, your engine would be at temp in much less time.

They car is also going to be in a cold mode to warm components up. That's going to be a less efficient mode of operation. If op only drives in warm up it's going to have a large impact on mpg

Still better to drive it while warming up than to let it sit in a parking spot while warming up.

Oh yes! Sorry if it sounds like I'm saying you should let it idle to warm it up. You will definitely have to drive any car before it completely warms up.

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I used to game my Fusion Energi in the winter. I'd preheat, but that's not too effective with 110 VAC, and then use only the heated steering wheel and heated seats to get to work, about 28 km for me. Sometimes I would make it without gasoline, but if the gasoline engine kicked it, it was screw it: full heat.

Even though I'm in Michigan and it's usually -3°Cto -12°C, with the windows closed, the steering wheel and seat combination were actually quite effective.

Run 220 to the garage?

If I every buy a plug-in hybrid of my own (versus just having a company car), then I will.

I wish all garages had them. It’s so much better for air compressors, electric heaters, and most recently plug in electric cars.

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it isn't the heater that is the primary cause of the reduced mileage, it is that the engine has to stay on more often to keep the engine at operating temperature. air conditioning cooling saps a lot more power/energy than heating.

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First winter with my Prius. Honestly considering I was looking at mid teens per gallon in my old car, 30s is still a treat. cause I'm in Canada and were getting -25C here this last week....would love a hybrid

If it makes you feel better. I drive a Ford F150 thats pretty big. I love it cause occasionally I do have to use the bed. But I would love to have a Tesla it really any nice looking hybrid or electric car.

I'm waiting for someone to make an electric pickup, Tesla has made some noise about developing one.

17 points · 6 months ago

Musk tweeted a week or two ago that it's on the to-do list for a couple years from now. He's definitely been thinking of how he'll do it

I think mini-truck would be the way to go. They're no longer on the market, but it seems like there is still demand. And any kind of payload or towing would kill range of an all electric, so limiting that by the size of the truck itself makes sense to me. Wait and see if guess.

Massive demand for a small pickup. The toyota tacoma just keeps getting bigger and nissan's offerings are getting larger as well. An S10/nissan hardbody/toyota hylux (90s) with an electrical powertrain would absolutely kill it.

Toyota needs to go back to the small Tacoma.

I haven't looked at the dimensions, but a friend of mine recently said the new Tacoma is the same size as the original T100/Tundra. I know we love our big trucks over here. But a small over the wheel truck bed like the old hilux would be an amazing buy.

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An ICE truck that small will never be produced for the US market again, they can't meet emissions standards

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Take my money now. I've wanted this truck for years.

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So, an electric el Camino?

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A rather high base price of $52500, but this truck looks really cool.

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4 points · 6 months ago

Recently the F150 got some aftermarket options. I'm looking at doing this to mine.

I drive a ford excursion, v10 gas, lifted, bigger tires and get about 10 to 15mpg.. but I payed $3500 for a low mileage car, saved the earth a lot of mining and manufactoring costs, camp out on it and... i chose less income to be able to work from home, so I only put less than 1k miles a year on it.

Drive a 2014 Freightliner Cascadia with a 15 liter diesel. Get about 6mpg. Put about 150k miles a year on it.

That’s enough fuel to power ~70 Priuses a year

The real kick in the nuts would be if you hauled Tesla parts,

A prius weights what? 3000lbs? My truck weighs 80,000lbs. So I move about 25x more weight a mile at 6mpg VS a prius at 50mpg. So which is really more efficient and getting shit done haha.

If you define efficiently as the amount of useful work per fuel used, the total weight of the vehicle is irrelevant. Only the amount of cargo matters (it could be weight, number of people, etc.) If your truck holds 30 tons of freight that's 180 miles per gallon per ton. A Prius would have to hold almost 4 tons of freight to get the same efficiency, but I suspect the payload rating is less than 1000 lbs. Your truck uses a lot of fuel, but it does a lot of useful work, which is the definition of efficiency. Large passenger vehicles on the other hand ultimately move the same number of people as a Prius most of the time, so they are not efficient.

CSX claims 500 miles per gallon per ton for rail freight, so your truck isn't even that much less efficient than a train, and it's probably faster.

8 points · 6 months ago · edited 6 months ago

I could argue that there are some other factors that matter than just cargo (23 tons is about my legal limit depending on fuel load). A good fifteen hundred pounds is probably the weight of my sleeper compartment which pays off immensely for my operation by allowing me to not have to shell out 50-100 bucks a night on a hotel. And yea deff faster than a train but trains have some advantages too as far as how many people need to be paid to move X amount of freight etc.

Edit: numerical correction

What I REALLY want is smart cruise control where I put in what ETA I want to a destination. Then using road topography my truck will automatically slow on level ground and uphill sections if it calculates it can gain the time back it needs to make certain arrival times on downgrades.

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I drive an F250 with a six liter diesel. I could carry a hybrid in the bed. It would still take 10 mins for the heater to warm up. Luckily, it has heated seats.

I don't understand this. I drive a 5.7L challenger and it goes from closed cycle to open in 30 seconds and is warmed up to operating temperature in about 2 minutes. And then I get 25-28 mpg which I feel is acceptable for a V8. Why do all these other cars take so long to reach normal operating temperature?

You get 25-28mpg from a large V8? I'm getting the same MPG from a 1.6L I4 turbo. Is it the turbo? Or is something wrong, maybe? I don't know much about cars.

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3.4k points · 6 months ago · edited 6 months ago

It's a comparison between a new car and a 14 year old car. The old car will have an engine in worse condition which will reduce efficiency, so it's not a useful tool to determine the differences in real world economy between hybrid and petrol engine.

If it were a 14 year old hybrid that was more efficient than a brand new petrol, then I'd be impressed.

Came in here to say I'm not an engineer, but that comparison seems skewed at best.

you had my interest at "atkinson cycle"

110 points · 6 months ago

Atkinson cycle just means the engine is capable of changing the the intake and exhaust valve timing. In the Atkinson cycle I believe it leaves the intake valve open longer during certain conditions, like cruising on the highway. You lose peak power but gain efficiency. The technology was original made for hybrid vehicles. But interestingly my pick up (a 2017 Tacoma with a much bigger engine than either of these vehicles) has an engine that is capable of Atkinson mode. It's rated for 22 highway. Since I'm hardly ever cruising on the highway without full load I usually see about 20. Still not bad for a gas truck with 600+ pounds of people and gear in it.

Edit: also re reading the comment and your user name I'm realizing you probably weren't asking what Atkinson cycle was and can probably explain it better than me. But I'll leave the comment just for my experience with an Atkinson engine.

It's honestly ridiculous the mileage that new trucks get. I get about 16 mpg (18 highway, but I don't do much highway in my 11 year old SUV. My previous even older car averaged around 12 mpg.

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Focus on the slope of the lines. This post is about the affect temperature has on both hybrid and petrol cars. From the data, hybrids efficiency is negatively impacted by cold temperatures at a greater rate than traditional petrol cars.

It would be great if the petrol car was also built in 2017, but I believe we would see similar slopes.

TIL hybrids are noticeably less efficient in cold weather. Thanks, OP.

Viz Practitioner
6 points · 6 months ago

I don't think it's because hybrids are "less efficient", it's because the heater operates by passing air over the cooling system for the engines coolant, which is only hot when it's burning fuel. The chart is basically demonstrating the impact that using the heater has. In a gas car, the coolant is already hot so running the heater doesn't expend much more additional gas, but in an electric vehicle they're burning gas for the sole purpose of operating the heater.

I'm not a mechanic, but I'm pretty sure that's what's going on here.

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This guy gets it. Mpg stat alone is the most boring thing on this graph.

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278 points · 6 months ago

Also, new petrol-only engines are better than a 14-year-old engine. Not that much, obviously, but it should be adjusted for.

43 points · 6 months ago(18 children)

Your Mazda 3 engine runs direct injection at 13:1 and is probably paired with a 6 speed transmission.

Corollas had a 4 speed and back then engines didn't have all the fancy timing tricks that let them do a longer expansion stroke than the compression stroke (atkinson). It's unlikely a "109hp" version would be much better though a lot of this comes from the car the engine is in and there's not a lot to be gained if the engine isn't overkill in the first place.

You have to be a bit careful, there were some very high mileage cars made in the 1990. Yes today’s engines are more efficient, but over cars are more powerful, heavier, have bigger electrical draws, and have larger tires which all hurts.

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My 2.3L 2005 Mazda3 got, at best, 23 MPG. Didn't matter if you had AC on, if it was -30F or you were doing 100 MPH. 23 mpg.

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Well. I would like to see this chart with x as age of each engine, instead of temp.

I know electrics’ carbon footprint improves over time as the grid gets cleaner. I believe an ICE’s efficiency declines with age.

13 points · 6 months ago

I have a 1995 Suzuki Sidekick JLX. It got 30 miles to the gallon when I got it (2004). It gets 30 miles to the gallon now.

It does get better gas mileage in warmer weather, but not by much. In near freezing temperatures, it gets around 28 miles per gallon (280 miles per tank).

In 4 wheel drive, it gets half of this. Also, no difference that I can discern between city and highway driving..

Yup. 1999 Saturn SL (standard transmission) averages 41 MPG; it outperforms many hybrids of today and cost (back then) $9999.

Keep the oil topped up and it'll keep purring for years to come. I miss my 1997 SW2.

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Where I am (Canada near Ottawa), it's not just the temperature that affects gas mileage, it's also the winter tire's increased friction, the snow/slippery conditions, having defrost on, etc. If you only travel short distances, then the engine doesn't have time to warm up and temperature is going to affect you a lot more than if you drive longer distances; similarly, having the car in a heated garage will make a difference, and the heating has an energy cost that's not taken into consideration with gas mileage.

My winter gas mileage is about 20% worse than my summer gas mileage for my 2013 Hyundai Elantra GT.

Speed has a bigger impact than temperature.

Yes, this was and is my experience also. I used to live in Fairbanks.

By heating I am assuming you mean plugs to plug your car in (for an oil pan, engine block, transmission, and battery heaters) while you are at work or shopping or at home, unless you have a garage, which I will assume central heating..

My winter gas mileage was 50% of my summer mpg. In Fairbanks, it was advisable to always have your 4 wheel drive on. I always had mine on at any rate.. so, between 120 and 150 miles per tank. Awful.

I live in Florida now, and it is a steady 300 miles per tank. For the past three weeks, it has dropped to 280 miles per tank.

I am a grandma driver. I start off at a gradual rate, coast, don't really ever go over 65 miles per hour. Pretty good for getting the most mpg out of any car. Its a 23 year old car, so gotta treat it well.

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Also depends on how well they're maintained. My work car has 220k miles on it and has seen a negligible loss in MPG (Within 1MPG). Still get about 34MPG highway and 30MPG in mixed use. Sticker MPG claims 38MPG possible for highway, but even on long trips I never saw better than 34-35MPG even when it had under 100k miles.

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Well, what’s the advertised average MPG for a 2017 Toyota Corolla? Looks like it’s 28/36 which doesn’t look too much different from the data plotted here. (2004 Toyota has the same stats.)

So while I agree it’s not a good apples-to-apples comparison, it doesn’t look like fuel efficiency degraded that much, which is a good selling point for Toyota.

Best comparison would be to a hybrid to non-hybrid version of the same make and model.

A modern corolla makes about 30 more horsepower than one in 2004 though, for about the same mpg.

It's also much safer and has stricter emission controls.

17 points · 6 months ago

And more weight. Don't forget the weight.

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Really? I'm shopping around for new cars right now, and their fuel efficiencies all seem to be comparable with my 20 year old car (comparing small sedans, non-diesel, non-hybrid).

By spec, it's 28 city, 39 highway, which matches pretty well with my data from the last 5 years of mostly urban driving:

My fuel efficiency from 2012-present. Haven't correlated it with temperature yet, but I wouldn't know how to isolate the outdoor temperature from the blend of fuel I'm getting, or other factors like that.

Yeah there's a lot of stuff to go wrong, but outside of a poorly maintained engine/older engine with mechanical faults (which would result in higher fuel consumption) I'm not sure that simply age alone is enough to deteriorate efficiency.

I'm in the same boat as you, 14 year old car, and on average I hit the spec efficiency.

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It's the phone/battery problem.

Everyone is pretty OK with ~25-35 MPG. Any more cost spent to get that MPG up makes the car more expensive overall and sell worse. Just like how we could make bigger phones with great batteries, but choose to make them smaller with the same battery, cars are generally made to conform to certain MPG standards and then they focus on other things.

30MPG is pretty cheap to run, so instead of making cars get higher MPG they've used efficiency gains to add more bells and whistles and make the car bigger and safer.

Sure a modern Carolla doesn't beat a 2000 Carolla much in MPG, but it's a bigger, safer, more comfortable car and it's still relatively cheap to buy. Would you buy a car the size of a 2000 Carolla today just to get an extra 15 MPG when another much more spacious car was next to it for the same price?

The problem with renewables getting cheap is that it's pushing oil to be cheaper too to compete. Cheap oil means MPG is low priority.

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Original Poster132 points · 6 months ago · edited 6 months ago

You're right, there's a lot of improvements that will affect fuel consumption.

It's sometimes hard to communicate efficiently in short titles. What I wanted to emphasize was that these are actual data sets, not factory test results.

It's certain that my driving costs have gone down considerably by switching to a new car, and the hybrid technology is one part of the equation. We also must consider that the IONIQ has a much smaller drag than the old Corolla, and that the older car had much more wear (it had 100' miles behind it last year).

But another thing I found really interesting was that the hybrid mileage is so much more temperature dependent. I hadn't anticipated such a large variation.

Hey OP wanted to thank you for taking the time to graph and post your data.

I know we're having a lot of discussion here and I don't want that to take away from how glad I am you contributed and facilitated these discussions 🖒

It's because batteries perform worse on very cold temps probably

And you have to run engine for heat.

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Is it temperature dependent or heater dependent? It took me a while to realize that the heater in my gas-powered car uses waste heat, but my plug-in hybrid has to use battery power to make heat while in electric mode (EV). Now I only use the seat warmer in EV (which has a much lower impact on my EV range than heater does) and turn the heater on after my EV battery drains and the car is in hybrid mode - about 5 more miles for my commute. Winter temps here are in the 30’s and 40’s in the morning, so just using the seat warmer is tolerable if I wear gloves.

Its dependent on how warm you want the cabin. If your dressed for winter you can get away with a cooler cabin.

Heated Seats + Wheel should be enough even in -20C.

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A follow-up question: are the mikes the same type of miles on both cars (i.e., city versus highway)? It is my understanding that hybrids get better gas mileage when driving in a city versus highway miles. If the ratio of city to highway miles are different, it could distort your data.

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Original Poster5 points · 6 months ago · edited 6 months ago

Yeah, like /u/dalelatrend said, it's mainly my commute route, so most of the miles are on the same road, in the same hours of the day and with the same amount of traffic.

The car automatically switches between the engine and the electric motor, so I can even coast on the highway with the electric only, but it does get much more fuel efficient in the city.

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OP said elsewhere that it was his regular commute (longer trips for vacations removed).

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120 points · 6 months ago · edited 6 months ago

No, it's investigating the temperature dependence of gas mileage for two cars (as the graph title says).

As the owner of a hybrid who had the feeling that gas mileage was worse in the winter (with no hard data), I'm impressed.

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This shows efficiency across different temperatures. The obvious conclusion is if you live in Alaska or North Dakota, a hybrid isn't going to give you nearly the advantage it would in San Diego.

Everyone already knows hybrids are more efficient (and that's not going to change if you got a 2017 Corolla). This is showing how that efficiency gap changes across temperatures.

23 points · 6 months ago

Yeah, WTF these comments are like i'm in the twilight zone. A 2017 IONIQ is more efficient than a 2004 Corolla even if both were brand new. The interesting data here is how temperature plays a role in efficiency.

Fr, there are a lot of factors in determining gas mileage and age of the engine is one of them.

Look no further than the 2000 Honda Insight. I owned one in 2014, and could routinely turn over 80mpg in the summer, and over 55mpg in the winter.

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99 points · 6 months ago

It's raw data. No comparisons were made, no conclusions stated.

OP graphed the data from two cars (s)he had available.

It's not their job to impress you.

However, it IS bad practice to visualize raw data in a way with misleading implications. Happens a lot in business, unfortunately, but it's professionally irresponsible for the analyst. The choice of visualization has underlying intuitive suggestions. In this case, graphing the two trends on one graph suggests it's reasonable to compare them. But it isn't.

If someone graphed the price of apples with the price of oranges, there'd be complaints too.

EDIT: Also the thread title has the word "comparison"

I think the main transgression is that the title draws attention to the hybrid/petrol variable and completely neglects to mention that there is an age variable.

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Original Poster3 points · 6 months ago

You have a point. Should have pointed that out in the title. I wanted to have a short title, but it obviously confused a lot of people.

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Spot on. This data, although interesting, has no real comparative value or point to make due to the variables

What this really shows is that hybrids also tend to do relatively worse in the cold (as they don't shut off the gas engine as much in cold weather).

We already know a 2017 Ioniq (the most fuel efficient car on the market) will get better mpg than any ICE car based on government fuel economy data.

Temp vs mileage is data that can be viewed for both car types, just not against eachother. So there is valid comparisons in this

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There is definitely a comparison made, seeing as there is 2 data sets, and while no conclusion is stated, it is implied.

Are we looking at the same graph?

To me it clearly shows that the higher the temperature the better the mileage.

In fact, the second data set is only there as to show the phenomenon is not limited to the new car

And that it impacts the hybrid more than the gas.

That too

Thank you. I feel like I'm taking crazy pills.

this here, however once it reaches point beyond ideal Temps (I'd imagine into the 120+ degree range that we would see drops in efficiency.

no, no. you can clearly see that the relationship is linear. you can safely assume the improvement in mileage continues to infinity.

I know this is sarcasm, but you can see the spread in plots already beginning at 65 F, albeit not by much. It's at 120 that you see changes in the way engines ability to cool is dulled and things change a lot.

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I recently changed from a 2004 2.2 X Trail diesel to a 2015 2.0 diesel Mondeo and all other things being equal my fuel consumption has gone from around 34mpg to 40mpg. Not as much of an increase as I hoped.

My mum just got a Kia Ceed and that’s doing an average of 55mpg

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8 points · 6 months ago · edited 6 months ago

I have a brand new petrol. How would I go about measuring this? (VW Up)

edit: sorry for asking simple questions

Miles driven divided by gallons used.

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2 points · 6 months ago · edited 6 months ago

Incidentally, if you wanted to skew the data in the opposite direction, you'd use a Tesla SUV. You could think they're to electric cars what a tank is to gasoline ones.

2 points · 6 months ago

Still holds up. I have a 2013 Mazda 3 that I drive sedately and it regularly gets 30-36 depending on city or highway.

Agreed for the most part, but are modern engines a whole lot different? I feel like we've reached the peak of gasoline engine efficiency. Maybe I'm biased in my thoughts because my 26-year-old Mazda 626 still regularly gets 30+ mpg, and I see that number thrown around a lot for modern cars.

That's feature and safety bloat playing a huge part though right? One of my first cars was a Suzuki swift 83 or something and it got 60+mpg. There were tons of crazy fuel efficient cars in 70s and 80's.

Now that every car has air, heat, 4+ airbags, noise deadening, etc I would assume that plays a significant part.

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Really glad this is the top comment. Data means nothing without context.

I thought the interesting part was how much effect temperature had on fuel efficiency that there was so much more consistency in the ICE and such a variance on the hybrid.

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I'm less interested in comparing the two cars, (as other comments have pointed out it isn't really a fair comparison) but instead comparing their variance. It seems the hybrid is much more affected by temperature for some reason.

battery performance degrades significantly in the cold (you may notice your car doesn't start up as quickly in the winter) - so I'm assuming that's where most of the difference comes from.

75 points · 6 months ago · edited 6 months ago

In addition the car will run the engine more often to provide heat in the winter.

I'd be interested how the a/c would affect things as well. Too bad the temps in OP's area never seem to get high enough for it to be needed. But I wonder if you would start to see it curve downward as you got into the 80-90 degree range.

Hybrid A/C systems are electric and they are very efficient mpg on A/C isn't much of a factor. Just keep it some where in the 70 degree range and don't park in the sun.

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How does heating in a hybrid work? Like if you stop the car for 5 minutes will the engine go on and off to heat, or does the battery power the heater?

8 points · 6 months ago

If climate control is on and it’s cold in my hybrid, the engine will turn on until it’s warm than turn off again if it wasn’t running already. If it’s already warm inside and I’m idling, the engine won’t turn on.

10 points · 6 months ago · edited 6 months ago

I have a 2014 Ford Fusion SE Hybrid.

Turn car on. It silently starts and is ready to drive. If the climate control system calls for heat, a couple seconds later the engine will start. The engine will stay on for about 5-6 minutes until it is fully warmed up, whether you are driving or not, then will only turn on as needed for heat or power from there. If you're not using the engine for power, you'll find it turn on for a minute every few minutes to stay warm. If you're actually driving the thing, the engine will run enough to stay hot anyways, so it's just those opening minutes that hurt your efficiency that way.

All heat comes from the engine.

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I think that's the point of the post

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Might not be a fair comparison, but I’m still pretty blown away by how much the temperature affects the mileage. Never knew it had that large of an impact.

15 points · 6 months ago · edited 6 months ago

It's the hybrid battery taking a hit from the cold temps.

Source: Prius owner

Edit: I could be wrong lol

Probably that the gas engine can heat the car interior basically for free using engine waste heat. The hybrid needs to actually use power when you run the heater.

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I was mostly surprised, the fuel consumption goes up with temperature, at first. But then I realized how the local unit MPG works. It is apparently the other way around compared to how we measure fuel consumption in the rest of the world.

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Original Poster15 points · 6 months ago · edited 6 months ago

Sorry. I'm also mostly used to L/100 km, but the last time I posted that, I got lots of complaints from US redditors.

Tell them to shush and realize that L/100km makes a lot more sense and correlates directly to money spent.


I say: Let them complain.

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27 points · 6 months ago · edited 6 months ago

I made a thing! Hybrids often cost a bit more than a non-hybrid of the same class, and my little calculator gives you a rough idea of when your investment breaks even.

Feel free to let me know what you like and dislike about it.

Can you make it use SI units?

While at it, keep in mind it's more common to use l/100km with SI, rather than inverse of that.

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Hybrids have higher servicing, parts and battery costs too.

You should factor in more than just fuel cost in this type of calculator.

Basically it's cheaper to drive an old small engine-ed vehicle with a conservative driving style than pay up for a hybrid.

If your doing huge mileage hybrids can save you money though - taxi's e.t.c.

It is unlikely that the battery will require replacement within the expected lifetime of the vehicle. Maybe for old Prius' but not for modern hyrbids.

That's not right.

Camry hybrid Taxi's (on the road ~12 hours a day) here in Australia need a replacement battery after 3-4 years. My old's mans got ~12 taxi's one just needed new battery @ 198,000 km on the clock.

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My hybrid has a lifetime warranty on the battery, but the battery is expected to last the lifetime of the vehicle.

I have to change my oil less than my gasoline car, my brakes are still as good as new after 2 years.

I haven’t had any major maintenance, so not sure what costs look like.

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You may want to reconsider plotting the data as L/100K to avoid curvilinear relationship of MPG

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I wouldn't quite call this a fair comparison seeing as the cars are 14 years apart. Take for example my sister's 2016 scion iA, 1.5 liter gasoline engine/6 speed that averages around 48 mpg.

Hybrid tech hasn't made amazing leaps and bounds in the past 4 or so years, whereas gas engines have been pushed to match the hybrid trend

(See mazdas new HCCI engine)

That being said, this data is interesting as long as you can understand the reasons for variation.

Edit: just realized the main comparison is mpg/temp and not a direct comparison facepalm

I did however just ask my sister what her mileage was for December and she said that it did not change from the summers numbers by anything significant, so I will let my points above stand.

My 2017 iA averages 37 mpg. 🤔

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46 points · 6 months ago · edited 6 months ago

Averages 48? Including city driving? No way.

If you’re solely on the highway doing < 2500 rpms at 60mph for a few hours and it’s fairly flat and somewhat cold, sure, I bet you could get up to 48. If you’re doing city driving at all I do not believe it for a moment. I have an 07 Mazda 3 and twice have I gotten 40mpg, both times were when I filled up, immediately got on the highway, and filled up immediately after getting off of the highway.

Edit: Cannot understand why people are reading this and thinking the intent was "my 11 year old car that weighs more and has a bigger engine can't high 48 so hers cannot either". The point was the only times I ever got unusually high numbers was when I spent the entire time on the highway.

I might be wrong, but I don't think the 07 Mazda 3 had GDI. The jump from EFI to GDI is similar to the jump from carburetion to EFI.

For example, my car has a 1.6L EFI engine from 98 and gets 32mpg AVG. That same engine , were it carbureted, would likely average around 25mpg. Whereas with GDI, I could easily be pushing 38mpg.

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mazda 3

I think therein lies the difference

Also, this is elpaso, and her commute is about 30 minutes mix of city and Highway

And to be fair, i have a lead foot (I'm a race driver, what can I say) I would probably have worse mileage.

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I think people lie about their mileage like short men lie about their height. If you drive mostly in suburbs over flat terrain, and call that "city" driving, then maybe you can get close to EPA "city." Otherwise, forget it. I drive primarily in San Francisco...up and down hills, lots of start/stop. My Mazda 3 gets about 22.5 MPG city. EPA city estinate is 28. On highways, I drive about 70 MPH, so maybe 28 hwy MPG. Over 30? Never.

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I can agree that it is not a fair comparison, but the iA is a ~2400 lb car while the Ioniq clearly has to pull around an extra 550-600 lbs (depending on options, and not including driver, lol).

An old CRX HF or a slightly less dinosauric Civic VX can get close to 48 mpg as well, but neither of them will probably pass current NHTSA standards.

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ITT: people comparing the cars against eachother instead of comparing the cars against themselves at different temperatures.

OC: 3
Original Poster46 points · 6 months ago · edited 6 months ago


  • Python with matplotlib to plot data

  • Microsoft Excel to store data over time.



As a follow-up on my previous post, I have compared the mileage between my last two cars; a 2004 Toyota Corolla and a 2017 Hyundai Ioniq Hybrid.

I mainly commute to work, and have extracted the data from the same date range in 2016 (old car) and 2017 (new car). With approximate the same power from the two petrol engines, it is quite interesting to see the effectiveness of the electric motor.

Some observations:

  • While the Corolla has a higher spread in the data, I believe this comes from the higher filling frequency and shorter distance driven per fill-up.

  • The hybrid car has a much larger temperature dependency, but is still much better than the pure petrol car at all temperatures shown.

  • Temperatures around 50 F are very rare where I live.

+1 for the other units. Km/L isn't really the one we use though. Typically it's L/100km. Great visualization anyways!

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Why truncate the Y axis? This makes the graph looks like a scam.

Also, metric units are liters per 100 km, not Km/L.

OC: 3
Original Poster12 points · 6 months ago

Truncating the y axis is a problem with bar graphs, I'll agree, but this is a scatter plot and it's not like I've hidden the units. I had a choice and went with the option that maximizes the amount of plot used for data.

I use L/100 km myself, but some people feel that it's more intuitive to see an increase with temperature. I used L/100 km previously and got complaints then as well! 😂

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While not super helpful comparing the two cars against each other directly, which is what many people seem to feel the point of this was, comparing the difference that temperature makes in the gas mileage of the two different cars is extremely interesting.

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Are you just comparing gasoline used, or does the hybrid car come fully charged? ie. then it has a supplementary power source that can be used to reduce the use of the gasoline engine, resulting in lower MPG. This them makes the comparison meaningless - unless the battery is only charged by the internal combustion engine.

How did you account for the battery in the hybrid car that sometimes powers it?

OC: 3
Original Poster25 points · 6 months ago

That's a fair question. It's unfortunately not a plugin, so all the energy in the battery comes from the regenerative braking or the ICE.

OC: 2
9 points · 6 months ago

Thanks, this was my question as well. Regenerative braking is pretty impressive stuff!

7 points · 6 months ago · edited 6 months ago

I don't think the 2017 ioniq was plugin The chart says "Hybrid" not "Plug-in Hybrid" so all battery power originates from burning gas.

17 ioniq comes in a conventional hybrid, PHEV, and BEV variant.

5 points · 6 months ago

You're right. I still think this refers to the Hybrid because that is what it says at the top of the chart.

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It’d be interesting if you factored in a depreciation / mile cost into it to see if it brought the trends much closer.

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I think a lot of people are missing the fast that batteries discharge much quicker in the cold, requiring more input from the gasoline engine to charge it.

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What is the tco of the two in that period?

How much different would the acquisition price be of both of them at the starting point if you were to purchase the 14 year old car vs the new hybrid?

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Very interesting. I've always heard that in theory, you would get better gas mileage when it's cold outside because the gasoline fumes are more compressed when it's cold out

Never made since to me though because it always seemed like gas fumes expand more when warm/hot, therefore I thought that your gas mileage would improve with temperature.

34 points · 6 months ago

It also takes quite a while for the engine to reach ideal temperature. My gas consumption is through the roof during the winter since I'm mostly doing short trips and the engine doesn't have time to heat up and function properly.

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Actually, that relationshipus a really interesting one, especially when it comes to modding cars. You hear of people, who want more power, adding cold air intakes. There are designed to pull the coldest (and therefore most dense) air possible, so that you can burn as much fuel as possible with each power stroke of the engine.

But, what you also have is people, who want better fuel economy (hypermilers), installing warm air intakes. When you take in warmer air, it's less dense, so not as much fuel can be burnt. This allows the engine to run at higher RPMs (more efficient up to peak torque, ~75% redline) for longer, giving better fuel economy.

So, for this aspect, warmer temperstores give better fuel economy, just as long as your driving habits are trained to match.

5 points · 6 months ago · edited 6 months ago

Isn't the fuel already in the cyclinder and whether the fuel is burned (completely) or not is inconsequential as it has already been 'consumed' by the engine? Or do modern cars adjust fueling based on intake temp? I can't wrap my head around the idea of something that causes an engine to have less hp would make it MORE fuel efficient.
Edit: () 2nd edit: Did a little research and answered my own question. In cold outdoor situations, the Mass Air Flow Sensor indeed makes a reading that in turn causes the engine to pull more fuel. Especially during cold starts/warm up. I feel like I knew this already, even though my brain wasn't accessing that info. I could see this WAI being counterproductive in warmer temps as your throttle foot will begin to compensate for less hp. Interesting stuff.

Modern cars detect the air pressure and temperature of the intake air and inject different amounts of fuel to match. Also power and fuel efficiency are different things. Most obvious example of this is an afterburner on a jet engine which increases power a lot but reduces fuel efficiency. In the case of cars, using a different gas cycle which uses less fuel and takes longer to extract all the energy is more fuel efficient, but drops the power.

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Fuel injection cars will automatically adjust the amount of fuel sprayed into the cylinder to make sure the mixture is correct. If the mixture is too rich you're wasting fuel so you get sooty exhaust (but the engine runs cooler). If you run too lean the engine can overheat.

The upshot if this is that if you have less intake air (because of temperature or high altitude) the car will inject less fuel to maintain the proper ratio of fuel to air in the cylinder.

<---' 06 tuned cummins owner. I know all about sooty exhaust and cooler egt's 😉 I'm frankly embarrassed by my own question as I basically knew all this but the wording was throwing me off. Edit: lemme rephrase; I didn't know that raising intake temps could help mpg. Everything else was a brain misfire. Live and learn.

The engine changes the amount of fuel injected based on the amount of air entering. There's a mass airflow sensor (and a few other things) that allow this. There's an ideal ratio of air molecules to gas molecules for a complete combustion, and the engine tries to stay around this ideal ratio. Dumping way too much fuel it wouldn't be a good thing at all, it's wasteful, it would start to clog things, your catalytic converter would go to shit, etc.

A cold or warm air intake doesn't inherently make your engine more or less efficient. However, a warm air intake, and therefore lower hp, makes it much easier for an engine to run in its most efficient way. I'll explain

There's an ideal spot for an engine to be in to run at peak efficiency. (Lowest "brake specific fuel consumption"). That spot is peak torque, wide open throttle. That means foot all of the way to the floor, and engine RPMs at about 75% of maximum. At that point, the engine will most efficiently convert the chemical energy in the fuel to kinetic energy. (Most is relative though, It's still only like 33% efficient...)

Anyways, having a hot air intake just makes it a whole lot easier to keep the engine at that perfect spot. With a really powerful engine, you could only keep it there for, like, a few seconds before you've broken the speed limit. Lower power gives more control, but ultimately It's still up to the driver to put the engine in the right spot!

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I always assumed my cold weather hybrid performance had to do with the energy used to power the heat. It always slopes off when I’m blasting it.

Speaking of which, as a Minnesota resident, I was disappointed to see the graph didn’t go below 15, to, say, -30F.

Lol, I just moved here and am disappointed not to see that range as well. This is my life now.

I wonder how far the data could extrapolate at negative temps, because OPs mileage gains were eroding as it got colder.

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Air is more dense when it's colder, and your car has to push through that. The added drag outweighs the performance benefits after a certain point.

I think you're right, the temperature difference, in this case, results in about a 10% change in drag, which correlates to about a 10% change in MPG.

Here's the formula for drag:

D = Cd x ((P x V2 )/2) x A

D is Drag, Cd is the drag coefficient, P is air pressure, V is velocity, and A is reference area.

We know the density of air (assuming 1 atm) and we can assume values for V, Cd, and A are constant since we're dealing with an average MPG. I'll assume 35mph. We can do calculations for both ends of the temperature range...


.5 x ((1.2041 x 352) x 1 = 737.5


.5 X ((1.3163 x 352) x 1 = 806.2

Or about a 9.3% increase in the drag value. With ~35 MPG on the warm end and ~32 MPG on the cool end, there is a roughly 10% decrease in MPG.

So the MPG follows the drag value almost exactly. Correlation does not equal causation and I may have done my math wrong (very likely), but it looks like you're right.

There are some other factors as well, cooler denser air helps the engine perform better, but at the same time different blends of fuel are used in different seasons. The cooler denser air charge is always interesting (when looking at fuel economy) on one hand, it does mean more fuel, so you get a slight hit to fuel economy, but on the other hand, the increased power makes acceleration easier which means less time accelerating which an help. Tires also react differently depending on the temperature. There are a lot of different factors to look at with temperature and change hence why it's not an exact 10% increase in drag = 10% decrease in fuel economy. It's all really interesting stuff.

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You get more power out of your engine when it's colder because your engine is burning more fuel.

Your engine is burning more fuel because cold air is denser, so it increases the amount of fuel in the fuel/air mixture to keep the engine running.

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OC: 1
3 points · 6 months ago

Op could be short tripping his car. Cold engines have to run a richer mixture because it's more difficult to atomizer the spray of fuel. It's less efficient until the engine is warm and can go into a closed loop operation.

All heat engines have a higher efficiency when the temperature difference is greater (so it's more efficent when cold outside). HOWEVER, based on the design of the car, the rest of the car is pretty cold too so there is more viscosity in the oil and thus more friction.

If you had a car engine at normal temperature, but had air intake and exhaust to subzero temperatures, it should theoretically be more efficient. (look up "ideal thermodynamic efficiency")

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As a guy who drives in an area where it regularly gets up to 110F+, I am jealous. You can really feel it. Not only that, at cooler temps, it makes more power because of the oxygen density in the same volume of air.

3 points · 6 months ago

Can you make the same trend in Gallons per mile so it is easier to understand. I think the thing most people care about is how much it cost to drive their car and the best unit for that is gallons per mile (or per 100 miles).

I wish the graph went higher in temperature. An EV/hybrid is going to have its worst efficiency when the temperature is cold (ptc / electric heater active) or hot ( electric air conditioning active).

Should be noted that there are two types of Hybrid Cars. Pluggable Hybrid and regular Hybrid. Pluggable can be charged and will run between 10 to 30 miles on the charge. Doesn't sound a lot but most people commute less than 30 miles. If Hybrid and EV cars replace just 20% of cars we would significantly reduce CO2 emissions, lower the prices of cars, and reduce our balance of payment.

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3 points · 6 months ago

That is what I would expect. Battery does not work very well below a certain temperature. So, the steep slope is understandable for the hybride. The Corolla has smaller slope and I believe that is sort of skwed since they use butane additives on gas during the winter months.

I don’t see how you can make this direct comparison and take any meaningful inferences from it. The two engines are from different manufacturers and more importantly...are from drastically different times in terms of technology. 13 years is quite a long time. The engines of 2017 are likely far more efficient. I think you should compare a 2017 hybrid with a 2017 version most comparable to the hybrid but petrol based.

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I don't think this is a fair comparison. The corolla is quite outdated and newer gas engines get pretty decent gas mileage.

Why is the comparison between a 15 year old car and a brand new hybrid?

a 2017 Toyota Corolla gets 30 city / 42 highway, that is a much closer graph than what you show.

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I’m more curious about the hybrid. Does it generate and store the electric energy while the combustion engine is operating or do you charge the battery from an outside source? This detail might skew the total energy consumed per mile if you have to charge the battery to get the results.

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2 points · 6 months ago

(in US) is it really typical to have it as miles per gallon? I know it only the other way around as L/km (in EU)

In most EU cars you can still get an MPG reading in your settings. Careful, though, a they'll show Imperial and not US gallons.

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How is the mileage calculated on the hybrid? Does it only include miles driven on gas? Or is it total miles (gas & battery)?

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2 points · 6 months ago

I just bought a 2009 VW Jetta SportWagen, 90,000 miles, inline 5, 87 grade, great condition. Took it to a mechanic first. Engine compression tested just fine. I was told I'd get 35mpg from the mechanic and seller. Site says 40 highway, 31 city. Then someone told me about this site. I averaged 23mpg measured over two tanks, combined driving, is exactly what I'm getting. Still happy with my new car. A lot of manufacturers "puff" their MPG numbers in unrealistic conditions.

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Fuck my face, the milage from my truck is literally not able to fit on this chart.

If you'll excuse me I need to go buy 80 dollars of gas for this week.

An additional real savings with hybrids having regenerative braking is the brakes need replacing something like every 100,000 miles rather than the usual 35-40,000 miles on a non-hybrid. So in effect every 100,000 miles you skip two brake jobs. That saves $800 to $1,000. Probably equal to or more than the savings on gas.

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