My 02 2500 12" lift with 41/22s would get 8 in town... 9 highway .... Its what I learned how to tune with... I was able to gain about 30% so i made it to 11-12 but I had to drive 80mph and no huge headwinds ... My 2006 2500 now gets around 14... but if you drive under 65 i bet it will gain a bit more....