Ok all you engineers out there.....lol. I have noticed that my mpgs really take a beating when the weather turns sub zero out. Now I know that the highly oxygenated air makes for great performance, and I do love that, but I wouldn't think the mpgs would take such a hit as well....????

I know when it gets cold it's harder to get "things" going, ie, greese and oil gets pretty thick. That's why I wasn't going to go another winter without changin' the diffs to synthetic....which I did. Last year when it got super cold, just trying to get out of the drive, my rear end would slip out just trying to move the rest of the jeep. Now with the synthetic I'm not noticing that....and it did get -20 last week.

Anyway....just wondering, other than letting the JK warm up just a few more minutes in the morning, what else do you think would be contributing to this...???

Thanks Much....

 

Cold weather causes the computer to RICHEN up the mixture. Subzero conditions would probably cause the mixture to stay rich constantly, to maintain drivability....this would cause fuel mileage to take a real hit.

 

This might be the case, if the all mighty PCM (and enemy of the people ) is programmed that way via its sensors, but as the air temperature drops the air gets denser which for a fixed fuel/air ratio will make the engine run leaner.

If the PCM adjusts the fuel ratio then it will run richer for a given throttle setting.

There are so many variables and tradeoffs between performance, MPG and emissions it's hard to know which way the system is biased.
There is one member on this forum from Penn State that specializes in Combustion and has worked for the big 3. He can probably shed some light on the subject.

I will say the performance on my JK is noticeably better when the outside temperature is above 100 deg. F

 

Winter gas has fewer BTUs than summer blend. That's part of your mpg deficit right there.

 

ahhhh the true alaskan vehicle.... I feel your pain. My last jeep i had bought in alaska and kept it up their for about four years. had zero problem and it rocked in the harsh weather. As soon as i drove it down to the lower 48 into the decent not plug your car in weather. It just started bustin seals and a gasket heads. Its crazy what the weather does up their to your vehicle and yourself

 

 

Another hit on mpg's is letting the vehicle sit idling to warm up.
The vehicle will warm up much faster if you start it and drive it. Yes, give it a minute or less to get the fluids to flow, then drive it.

 

Yeah, I don't like letting it idol very long but it's a little tuff getting in the damn thing when it's -30 below.......lol.

And just for that reason, I'm thinking about getting one of those little portable heaters for the inside that will come on when my outdoor timer turns on the freezeplug heater. Does anybody know how many amps the freeze plug heater draws?

 

I don't know if MOPAR offers more than one, but the one I know about is 400w @ 115v, which is about 3.5 anps.

 

Cold air and fuel = smaller molecules. Smaller molecules = more air and fuel packed into cylinders. Which explains better performance and crappy fuel mileage.