truckin151
Supporting Member
Its actually the opposite, with the overdrive gears in the the trans the 4.56's are actually around a 3.73 overall gearing on the highway or close to it (have to look up the math on it again), they will get you up and moving easier/quicker causing less work for the engine, and they put you right in the "sweet spot" for rpms vs mpg on the highway right around 2200rpm.