Cold weather = bad gas mileage?
 

Is my car just a freak, or have other people expierenced this as well? I've noticed it with other cars I've owned, but it seems by far the worst with my dsm. When the weather was warmer (30* and above) I was seeing about 23-24 mpg. Once Thanksgiving hit and the temps plumeted, I noticed my gas mileage went down to 18-19 mpg. I haven't really been letting it sit and warm up much longer than I did before, so I doubt that's the cause. I also haven't really changed my driving habbits. If anything, I'm easier on the gas pedal now than I was when it was warmer.

Re: Cold weather = bad gas mileage?
 

i saw this last winter with my corolla and i am starting to see it again.

i think it is normal, and i am not surprised to hear that it is more severe with a turbo'd car.

Aaron

Re: Cold weather = bad gas mileage?
 

Yes, that happens with any car. Usually drops a good 10%.

Re: Cold weather = bad gas mileage?
 

I noticed the change also

Think about what the computer reads and adjusts for.

Coolent temperature sensor.
When they go bad, car doesn't want to start. Why?

Thats because the computer adjust the fuel ratio when it is cold so it will start and stay running.

It could be that you are buring a lot of fuel before the engine is warmed up and that is giving you high gas consumption

I am guessing cold intake temps play a factor in this also.

Re: Cold weather = bad gas mileage?
 

I'm guessing it's something with the density of the air? I've also noticed that just cruising, I'm at a lower level of vaccuum (closer to 0 on the boost gauge) I suppose that could also have an affect due to the higher fuel pressure?

Re: Cold weather = bad gas mileage?
 

Correct. Cold air is more dense which requires more fuel to see the same air/fuel ratio as when the air is warm. I struggle to get 20mpg in town during the winter with the Evo where as I normally get 22-24.

Re: Cold weather = bad gas mileage?
 

The air has some to do with it, the rest is the grease in the wheels, tranny fluid, everything gets thicker and causes more drag. The engines run a little rich when it is cold out to make a little more heat too. That is why you don't have to put cardboard in front of the radiators anymore, unlike the old days of carbs.

Re: Cold weather = bad gas mileage?
 

Bingo!

Re: Cold weather = bad gas mileage?
 

I don't buy that. My car sure is stiff when I start driving, but loosens right up after a bit. Are you serious about running rich to make more heat? I've never heard of such a thing.

Re: Cold weather = bad gas mileage?
 

So rather than having a high flow K&N type filter replace with the stock cotton/ paper filter, less air flow = less gas used :D

Re: Cold weather = bad gas mileage?
 

Check your engine temp and make sure it coming up to the correct level. A cold running engine will stay in rich mode too long. Also check the temp sensor for the ecu to make sure it's reading correctly.

Also check your foot, cold weather makes it heavier for some reason. At least it does for me :wink:

Re: Cold weather = bad gas mileage?
 

Wrong. You will still get the same airflow because they are not that restrictive under normal driving conditions.

Re: Cold weather = bad gas mileage?
 

I still put a piece of cardboard in front of the radiator, its the only way i can get the car up to operating temp.

Re: Cold weather = bad gas mileage?
 

Interesting... Even at 0 degrees my Evo's temp gauge starts to move in about 5 minutes and that is when I can start feeling a little heat from the vents. It's warmed up in about 10 minutes. I have an aluminum radiator if that matters.

Re: Cold weather = bad gas mileage?
 

I don't know about you guys, but my driving is mostly 10-15 minute city trips. In the summer I'm up to full operating temp in a few minutes, but in the winter I may go ten minutes before reaching temp. I've always attributed most of the mileage drop to that. When I do long drives where my car is up to temp the difference is not as severe.

My miata has dropped 3-4mpg so far, but that might be due to all the wheel spinning action. :)

Re: Cold weather = bad gas mileage?
 

I never had a problem getting my dsm to operating temp, it was actually the fastest car I ever had to get warmed up. Brown- replace your thermostat if you havent, or make sure your fans arent on all the time.

Jet covered the main points.

Re: Cold weather = bad gas mileage?
 

Brownman, replace your thermostat like Peter said. All my DSM's have been able to reach full operating temp w/o a problem no matter how cold it got up in Duluth.

Re: Cold weather = bad gas mileage?
 

Most new cars (like 2G DSM's) will run the same coolant throught the bolck over and over till it's warm. 3S's (even 91's) do it, and so do a lot of other cars. Helps them warm up quicker. Also, one reaon they use more fuel when cold is that when it's cold, fuel atomizes poorly, so to get the same amount of burnable fuel in the cylinder, you have to put more in.

Re: Cold weather = bad gas mileage?
 

I don't care if you buy it or not, it is true. Your car loosens up some, but not as much as when it is warmer out. The engine and tranny loosen up to near normal, but the wheel bearings do not. Yes cars do run a bit richer when it is cold too. A smaller factor in play is the air is more dense so it causes more drag on the car going through the air. There is less drag on the tires though, since they are harder when it is cold out.

Re: Cold weather = bad gas mileage?
 

Winter fuel is also different than summer