why is it? seems contraintuitive. for the record i get worse MPG in 80's and above (AC) and 50's and below (heating). Edit: this is based on city commuting, pulse/glide, garaged overnight. rains excluded (much lower MPG).
My first guess is the impact of AC/Heat. Maybe the temperature affects the road surface in a way that reduces drag/rolling resistance?
weird how people don't want to talk about it. is it some sort of a taboo? case in point: the last 2 days were cold, daytime temps in high 50's/low 60's and i'm getting the best mpg since getting new tires a year ago, near 60 mpg. up to now, i averaged 55 mpg. now, my car is garaged, so it doesn't get a cold soak overnight, so this may make some difference.
Wish I had systematic data but don't. But my impression has been better mpg as temperature increases up until the low 70s where we start using the AC, which clearly negatively impacts efficiency. I had assumed lower energy losses due to lower friction, hysteresis, and cold start losses as temperature increases. Will pay more attention to see if we recreate your pattern.x
