drove from tarpon springs florida to montreal, quebec which is 1488 miles at 49.2 mpg highway which is 3.1 tanks of gas out of my 10.8 gallon tank. the average highway mileage for my 2008 Honda Jazz is listed as 34 mph highway and I did 49.2 mpg which is 15.2 miles over. all i have done is a ram air intake, exhaust, and a cam.