Alot of us are considering modding our vehicle to save money. Not much thought is given to a mod that will cost 400 bucks, if it will save 2 mpg. However, That 2 mpg will only save $0.03 per mile. Thus taking 13,333.4 miles before you "pay off" the mod, and begin to actually save money. On the flip side, many are concerned with how much mpg loss by adding larger tires, or a lift, or both, can affect them. Once again, using the same calculations, you can see how much your mpg will be affected. Use this calculator to help find how long it will take before a mod "pays off", or how much a mod may cost you.