I've been heavy defending yhe fuel economy on these when I had Mt 18 expy rwd. Now I have a 20 nav rwd and I gotta say, if your mileage socks, ch he your driving habits or get your truck looked at. I put about 650+ miles on it, and already avg 19+ mpg. On the hwy in eco, it avgs over 23 going about 72mph, the same as my expy. I purposely use the instant fe screen and it tells you how to get better mpg. I do t drive much in sport but the avg goes down slightly in town, but I don't gas it all the time and mpg avg does go down wildly if I idle it for more than 6 min.