[Porsche9]

For a point of reference in summer (hot as hell Phoenix) I get between 21 and 22.5 mpg. In mild weather it will move up to 23 to 24. Once it gets really cold (for Phoenix that's in the 30's in the early morning) it drops back down to 21 to 22.5. When it's hot it's the AC and when it's cold it just takes longer for the engine to warm up to an efficent operating temp. Throw in some more ethanol dependng on the blend being used in your area for the time of year and that will also impact mileage. I find how you drive it impacts mileage more then anything else. At the track I drop down into the low teens.