My wife car is a '96 855 n/a. It now has 220k miles and runs great. We have had it 1 1/2 years and fuel milage has always been 19/20 city and 24 hwy. I have seen and heard it should be 24 and 28. Last weekend, I had to make a 400 mile round trip and drove the car. I was by my self, so put the windows down and opened the sun roof, reset the mileage computer and took off. After about an hour on a 4 lane hwy, I was averaging 32mpg!!Never seen this before. Then I hit the interstate for another 140 miles at 80mph. Mileage dropped to 29.4!!! Didn't think the air made that much difference. On the way home I closed the windows and used the air. Stayed on interstate all the way home and averaged 27.9. My mind has not stopped trying to figure this one out. We have put 40k miles on the car since we have had it and just got the best milage ever. The only other thing I found, was the transmission was in the sport mode. The car is almost always in Econ. mode(to get better milage?), especially on trips. Has anyone else experienced this. We have a 700 mile trip this weekend, the car will be in sport. Could this be a predictor of a transmission problem? Again, the car runs perfect and is up to date on all maintenance.

Thanks,

Keith