Ok I know this has been a very know question and is everywhere in any forum but I need to ask. I have a 01 Auto and going to order a gear and t-lock for the car this month but I have two thing I am considering and what some opions ok I know they say to go 4.10 for the auto since you won't notice the 3.73 but on the other end if you use the car for highway driving go 3.73 for gas milage becuase about once or twice a month I usuall go driving about 400 miles for a break. I wanna go 4.10 for the car but how much difference will the gas milage be and what is the rpm range usually when you are on the highways.