under 2000rpms is where you'll wanna be. If you have a 4x4 I think the only other option is 3.54 gears, if you are only 2wd you could go down to 3.08's. There is a guy on here with 3.08's, but he has a single cab 2wd with some fairings and whatnot to achieve max mpg. Paying someone else to change the gears is not cheap either, so I would look into that. Another way to drop the RPMs would be to put on bigger tires. But that would increase rolling resistance and city mileage will go down but highway should go up. If you're only 2wd I would do it, but changing out two is $$$$. Maybe I'm just cheap