I agree with Carbking on surveys. I took a survey/statistics class in college and the one thing that I remember is tell me what you want to prove and I can write the survey to prove it. On a continuation of the mileage issue, I took a 2,500 mle trip with my Chevy Silverado truck and depending on the gas fill up(brand of gas), the mileage varied from 16.1 miles/ gallon to 19.3 miles/ gallon all highway mileage. This trip was in the center of the country with no big hills/mountains. I just set the cruise at 70 mph and relaxed to enjoy the scenery.