I have Toyota Prius and I recently have been doing some observing of my driving habits to see how I can get the best mileage. In addition to the tips already posted on this site, here's another one that got my mileage to 50mpg. Don't use the heater!! Pretty simple one, and hasn't caused me any great inconvenience. If I just turn the dial to the highest temp, but don't turn the fan on, I still get a little warmed up. And I still get good gas mileage (even with my car fully loaded for camping!!!). I hardly use AC so turning off the heat has really increased my mileage to about 5mpg more!!!