Of course, gas mileage will be affected by rear end ratio. When you are up in the high 3s or 4s your mpg will suffer. My choice has always been for the low 3s, even into the 2s, but I don't care about performance. If you want performance then you need the 4s, but highway driving will be limited. My squares have all ben 3/4 tons, so mpg is lousy with any rear end.
