My 08 F350 SRW with 3.73s averages 15mpg on the highway, and 12 to 13mpg in the city. If I drive normal I can get 17.7. I bought my wife a 09 F250 with 3.55s and it got 18.5 stock at 70mph. All this is hand calculated. 5 inch flopro, aFe CAI, and minimax on the 08. Haven't check mpg on my F250 since putting the parts on.