I didnt look at my last fill up.But its the best my truck has ever got in 10 yrs.But now that I think about it, it is very flat up here and could possibly add 40 miles to a tank , maybe. So when hearing others tell there gas miliage , now I know, to consider where they drive and the fuel they get.Im really into this because ive heard some 5.7s claiming 21mpg, well not in Bama where I drive.