1994 Mercedes E320: Summer = better mileage?
 

hello all,

A nice side effect of summer in California that I realized is now my car seems to be giving much better mileage than before even with the AC on most of the times. In previous months, the mileage was about 18-20 and now after summer started I dont see anything less than 21 and one time it was 25 mpg. Any comments on this?

1994 E320. I generally always fill upat Arco on Automall-S.Grimmer, Fremont, CA

Regards,
Kalyan

Yes. Warm air is less dense than cold air. That is why hot air balloons rise and airplanes need longer runway distance in hotter weather. Air resistance is a dominating factor in energy loss at highway speeds. I get about 10% better mileage when it's 80 vs. when it's 60.

The engine warms up faster during the summer, so it does not need extra fuel (e.g. "choke") for as long when started cold. If you do mostly short trips & city driving (which I suspect is the case, based on the posted MPG numbers) this is also a factor.

- JimY

Warm air is less dense than cold air.

Less dense == less oxygen

Less oxygen == less fuel needed for stoichiometric burn.

Winter/summer gasoline formulations make a difference too.