Does the ambient tempature affect the milage on the Highlander?

Oh yes. The ICE runs more in the winter and the batteries aren't as efficient when its cold. In the Summer I get 27-28mpg (sometimes 30+) but in the winter it goes down to about 24-25mpg (I use the seat heater more too).

The recent cold snap (only in the 20's) I'm getting 23-24mpg.

Seadog

Thanks Seadog. what is ICE?

ha, just figured it out Internal Combustion Engine...see Im not that Green (ugh)