Ive heard the putting lower gears in kills your gas MPG. Can someone explain this to me.

Here is my general understanding:

Say for example, that you have 3.55's now (most of us do stock) and was changed to 4.56's. On the stock setup the rear wheel should do roughly 3.55 rotations for every 1 rotation of the drive-shaft and with the 4.56 gears the rear wheel should do roughly 4.56 rotations for every 1 rotation of the drive-shaft.

Am i wrong in my thinking? Shouldn't it take less effort to get up to speed with the lower gears, ultimately using less gas under throttle?

 

pretty sure u got that backwards there. the tire will turn 1 rev per x.xx turns of the d/s

 

Now that would mathematically make more sense to me.

 

Lowering the gearing helps put the engine back in the power band and helps pull the added weight of larger wheels/tires and bumpers and all.

 

The more gear the less the engine has to work.............but unless you match it with the proper tire size...the extra RPM could cost you MPG.