One factor that comes into the mix is that colder air is more dense &  
so needs more

Gas to keep the FuelSupply Stoichi' ~ That DenserAir also produces a  
HarderWall to push

@ HiwaySpeeds ~ it's the reverse of those things that helps those of  
us living @ higher

alti's to get better gas milage than the folks @ SeaLevel. But  
WinterFuelMixes is probably

the biggest factor. Also keep in mind that the vol' of a  
Gal'OfGasoline @ 80� is 233.7CuIn

& @ 30� it is 227.0CuIn so you actually have less GasByVolume in your  
tank in the Winter

than in the Summer but I haven't really thought through what effect  
that might have on

the Air/GasRatio once that Gasoline gets Atomized by the Injectors.

        I also find that sometimes when the price of gas goes down that my  
MPGs go down

as well. May be some FunnyBusiness going on there ~

                                                        ORR ~ DeanB

On 30 Nov , 2012, at 10:24 AM, Rocket J Squirrel wrote:

> Well, as I mentioned my driving habits are no different now than they
> are in summer, and I should have also said I don't have any ice or  
> snow
> to deal with, at least not this early in the season. I get my gas at
> Chevron and it's normally 10% ethanol year-round, but I'm going to  
> fill
> the tank with 100% petrol next time, to see what diff it makes.
>
> --
> Jack "Rocket j Squirrel" Elliott
> 1984 Westfalia, auto trans,
> Bend, Ore.
>
> On 11/30/2012 09:21 AM, mcneely4@cox.net wrote:
>> Mr. Squirrel, I find it to be true of all my vehicles.  I believe
>> that one reason has to do with the consequences of driving on ice and
>> snow, which means more variable speed.  I also believe that fuel
>> formulation changes for different temperatures make a difference.
>> The slight difference in fuel density should mean better winter
>> mileage, but I guess the other factors obviate that.  For my Prius,
>> that vehicle runs the engine more to keep everything warmed to the
>> temperature the vehicle's brain prefers.  But that doesn't apply to
>> the Vanagon of course.  mcneely
>>