Varies with terrain, speed, wind, temperature, fuel (bio blend and winter blend), additive helps, cargo, idle time, transmission selector (D, M, or tow-haul), altitude, tires (psi, size), lift kit, dually.

if you think you have a problem we need lots more information. 16 is a normal in town average for average conditions and SRW stock wheel and tire with no lift, summer fuel with additive.