I used to have a 90 vette with the 6 speed. I removed the cat, installed a performance exhaust and a better induction system and consitently got 36 MPG. If I remember right it would turn just 1600 RPM at 65 mph. If I could get a different set of gears in my X and drop the rpms to the same as above I'm betting I could get 30 mpg in my X. Because of the need for performance BMW has the gears in the X set for acceleration vs. mileage. Is anyone aware of different gears available for the rear and front differentials? I now have 295/45/20 tires on my X and it dropped my RPMs but it still turns too many R's in 6th gear. I would put on yet taller tires but I've run out of room in the front wheel wells when I turn.