I mostly drive my wife's 1998 Corolla to work. It's a 147 mile round trip. The car has 195,000 miles on it. I used the cruise control on the last two trips I made, one set at 65 mph and one set at 55 mph. Set at 65, I averaged 38.5 mpg. Set at 55 mph I averaged 43.8 mpg. This car never ceases to...