cooler temp = more gas consumption

[Jacobzky]

is it just me or have you noticed anything about your gas mileage being more when its winter time?

 

[greasefingers]

There is an Intake manifold temperature sensor so the ecu corrects for variations here. The engine temperature is constant in all climates. So that basically leaves the winter gasoline blend as the culprit.

But no, year-round my v8 is very constant when it comes to fuel consumption. About +/- 1.25 mpg each time I calculate it. I never bother looking at the mpg read-out.

 

[Casper]

colder temps equal higher air density...to keep the proper AFR you have to add more fuel. In addition the running of winter mix fuel also has an effect.

 

[fourwd1]

Exactly, colder air has more O2, so more fuel is used. Although an EFI system should compensate and keep things fairly normal, where a carb won't.

 

[Thai]

See this thread: http://www.toyota-4runner.org/showthread.php?s=&threadid=32908&highlight=ethanol+and+winter

 

[Falls]

So true I drop about 1.5 mpg in winter. Also here in wisconsin we run winter blended fuel which always get worse milage . You can totally tell when they switch between summer/winter blend.

 

[Jacobzky]

ok that explains it, i thought my truck going through some changes. :

and maybe increasing tire pressure should compensate a little bit.

 

[CJ3Flyr]

Another factor is warm-up time... The warmer the outside temperature the quicker the engine warms up. When cold (below 150-170 coolant temp typically) the ECU runs in a warm-up mode. It's called "open-loop or closed-loop, I forget. The engine runs considerably richer and with less regard for fuel consumption/emissions when cold. If it's 50F the engine needs 5-10 minutes to warm up. If it's 5F it takes considerably longer and that equals more fuel.

If anyone in the group is lucky enough to have a heated garage they probably have the smallest changes in fuel consumption seasonally.

Yes, I know fuel formulation is a big player too...