Ambient temperature and fuel economy

[whizznbyu]

Am I just imagining this, or is there an inverse correlation between very hot ambient temperatures and fuel economy?
Seems to me the B5 is happiest when it's around 70F, not 99F.

 

[Lightflyer1]

Way too cold and way too hot, it suffers from my reading. Like you experienced somewhere in the middle it returns the best economy.

 

[jettawreck]

I almost always did the best tanks in late spring and early fall. Moderate temps, no A/C, before/after "winter" fuel blends, etc.
The ECU advances timing when it's cold (ambient air, fuel temps) but cold temps bring more rolling resistance and inefficiency combustion wise. Once those temps get hot enough the timing is advanced less.