Tell me I'm crazy....

[joekd]

I think temp itself does make a difference

Today I made a 300+ mile round trip, on the way down the temps started at -2 and only went as high as 8, I averaged just over 14 MPG on the way down, filled up at the same brand gas station and same grade (87 octane) but on the way back the average temp was just over 30, got ~16MPG. Pure highway both ways, difference in weight was about 120 pounds between the two trips.

 

[McDuff426]

There a lot of variables they all factor in, even a 25' difference in altitude would be a measurable factor. With an ideally functioning ECM system I could see ambient temperature effecting how long the initial warm up to "closed loop operation", while it's in "open loop mode" the engine is operating in a fixed fail safe mode, a good bit more rich so a more predictable level of performance can be obtained until the ECM can capture control and maintain "stoichiometric combustion management", can't just say til it runs right.

 

[D Hook]

also i always reset the tripometer when i fill it up, then divide miles driven by gallons put in tank

That's the best way to do it. Relying on the readout on the message center isn't very accurate.

To the OP: Yeah, you're crazy. But who isn't these days?

 

[43]

yeah my gauge stays on F for a long time then it'll start dropping like mad. i've calculated my milage manually and used the message center's average mpg counter, and it seems to be spot on.