I have a 2007 Toyota Tacoma four cylinder. in the summer it was getting 20 to 22 miles per gallon.
Now in the winter time it is getting 15 to 17 miles per gallon. This seems to me to be an excessive drop in gas mileage. Is this a “normal” drop in gas mileage or is this an indication of something wrong with the vehicle?
I don’t think I drive it much differently, though there has been an occasion for me to use four-wheel-drive; though not excessively.
I note, too, that in the summertime I had a canoe on the truck and possibly, conceivably made it more aerodynamic; though that seems odd.
Around these parts they have summer and winter blends of fuels. I know that one or the other causes a drop in MPG, as well as a slight rise in costs. (don’t remember which) This is California, and they feel doing that protects the environment by creating cleaner burning fuel. They may be doing that where you are too.
To me, that doesn’t look too unusual. During the summer, I get about 30-32 mpg typically on my Mazda 3, and in the winter it can sometimes drop below 25 mpg. Part of it is the winter blend gas (although the studies I’ve seen on this say the mileage drops 2-5%); more of it is traffic here is much more stop-and-go due to the weather. This site gives a number of reasons and the numbers.
In theory you should get better mileage in winter. Denser air means more air in the combustion chamber and more expansion during the power stroke. In reality most cars get worse mileage in cold weather. I don’t know if it’s winter blend fuel or just the fact the engine isn’t running in optimal (ambient) temperatures so it’s fighting to maintain warmth.
I can tell you that when I paid closer attention to my mileage, it dropped in winter as well. IIRC, my Honda Insight got something like 44 in summer and 38 or so in winter. I was getting about a 10% drop but you’re getting closer to 25%. When was the last time you had your car looked at? It might be something as simple as dropping in a clean air filter, a little more complicated like a new fuel filter or bit more than that like a fuel pump that isn’t maintaining proper pressure. After that, things get more expensive (like, say, a clogged catalytic converter).
Has it always dropped like this in winter or is this something new?
ETA, I also remind people that if they warm up their car for 20 minutes twice a day before they go anywhere, they’re burning off quite a bit of gas a 0 MPG and that’ll drop your average MPG quite a bit.
Check your tire pressure, I have always noticed a mysterious drop in that around when winter starts. I attribute that to humidity in the tire freezing out, but never found any confirmation, yet there it is year after year.
Doesn’t seem that mysterious to me. A gas occupies less space the colder it is, hence the lower pressure. I’m not sure if there are other factors at play here, but that’s the basic idea.
I asked a similar question about my Prius a few years ago. Unfortunately, I don’t remember the conclusion.
I was thinking that since the cold air is denser, and since the air-to-fuel ratio needs to be/tends to remain constant, more fuel is required to maintain the ratio.
It’s just something I recall a physics teacher telling me (perfect world and all), but as I typed it I kinda figured the computer and the MAP sensor and computer and all that would tend to even things out. I wonder what happened with carbed cars before computers and MAP sensors. OTOH, there’s special kits (K&N makes some) to bring the fresh air intake (the snorkel) to the front of the car to bring in cooler air rather than the warm air near the engine from wherever the manufacturer stuck it. Also, there’s even some people that will cool the air via the AC (that seems like a ‘no such thing as a free lunch’ issue since the AC will have to pump the heat out and tax the engine). Also, don’t forget, turbo chargers do nothing but cram as much air into the cylinders as they can. But I suppose that’s more about HP and less about MPG.
TLDR; physics teachers usually don’t live in the empirical world.
Specific to the Prius (and other hybrid vehicles), because of the difficulty of stopping & restarting the gas engine when it’s very cold, these vehicles have a set minimum temperature for this hybrid feature to operate. If it’s colder than that, the gas engine does not shut off as normal, but runs as long as the vehicle is running. That will reduce the mileage quite a bit.
And that minimum temperature isn’t all that cold. Here in a Minnesota winter, we may go for a whole month without ever reaching that temperature!
Actually, I’m pretty sure most engines are horribly inefficient in warmup mode (open loop mode, I think), but once they get warmed up thoroughly, they might be a hair more efficient in colder weather than warmer weather.
So if your driving patterns don’t involve a lot of trips long enough to warm the engine up in the winter such that it goes into closed loop mode, that may explain the mileage differences- in summer, it doesn’t have to warm up nearly so much, so it’s in closed-loop mode much faster.
[QUOTE=Johnny L.A.]
I was thinking that since the cold air is denser, and since the air-to-fuel ratio needs to be/tends to remain constant, more fuel is required to maintain the ratio.
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Gasoline engines need approximately 14.7:1 air to fuel ratio. Most modern engines have oxygen sensors that fine tune this ratio so that the amount of unburnt oxygen is constant. So if you drive at higher altitude or it gets colder, the ratio is automatically adjusted.
I agree with the posters above to check your tire pressure and have less idling or warm-up time. Also - it could be your thermostat. If the engine is running cold due to a faulty cooling system (which runs fine in summer) - it will give lower mpg.
The gas laws are computed using the Kelvin scale, and 40 to 80 Fahrenheit just isn’t much of a difference when both are over 400 Kelvin.
I too get worse mileage in the winter, and I’ve heard that it is the different fuel blend. Specifically, I’ve heard that there is more ethanol during the winter months. I do not know if that is correct.
My work van gets a couple of MPG less in winter, (17 mpg v 15 mpg) even though I never “warm up” for more than a few minutes and keep an eye on tire pressure, etc. Some other good points in the link above that I hadn’t thought of either.
It’s been several years since I tried this experiment but IIRC the cost of fuel was cancelled out by increased mileage per gallon - buying premium gas instead of the plebian stuff. Am I remembering correctly; is there any point in buying premium, especially in winter?
I’ve noticed the same thing in my truck. It calculates and keeps the overall mileage for me, and there’s a 2-3 mpg drop in winter. However, it’s only on the tankfuls that are mainly commuting (20 miles). The mileage for a recent 800 mile trip was the same as in summer, even though I had a full load of wood for the return. I think it’s due to not completely warming up (although there could be a blend-related component, since I refueled in different states).
PS. The tire pressure monitors scold me relentlessly if the pressure isn’t kept up. So it isn’t tire pressure related.
It doesn’t matter the density of the air. The engine control module is going to inject the correct amount of fuel to maintain the proper air fuel ratio. So more dense air = more fuel. On the other hand since for any given throttle setting more power will be generated you tend to use less throttle which tends to cancel out the more fuel thing.
Idling is what kills winter fuel mileage IMHO. You warm your car up? Kills MPG.
If your car has a trip computer try this. Tomorrow before you start the engine note the average MPG then reset the gauge. Warm the car up for two minutes then start driving. Watch the average MPG. It will take a long time to get back to near where it was. Zeros really bring down the average quick.
Then the next AM warm it up for the same time but reset the average MPG after the warm up and as you start to drive. You will be shocked at the difference.
Way back in the 80s, I went to a conference about fuel economy which involved an overnight stay. On the morning after, it was very cold and frosty, and half a dozen of us were standing in the car park chatting about what we had discussed at the meetings, while our car engines were warming up to defrost the windows.
It took a little while for the irony to dawn on us.
I doubt it. Premium fuel would still be the lower-energy winter blend. I go from about 28 mpg in the summer to 23-24 in the winter, a 14-17 percent drop. I mostly blame it on the winter fuel, but there is no doubt that the engine and transmission have more friction at low temps (at least until they warm up fully), plus driving in snow and slush creates more drag.