I just switched my axles out for some CVJ rebuilds, and noticed the rear end ratio etched on the bevel gear of the differential. I have a 2.66:1 rear end which must be close to the tallest that they made. I am not a slow driver (I put my foot into it fairly regularly) and have been getting 27-29 MPG in mixed city & country driving.

I have a friend with the same car and he is getting 22 MPG.

Changing the axles was not so bad. I don't think that changing the rear end would be much worse. I know that if that was the only contributing factor to the difference in fuel mileage. (which I know that it is not) this would contribute to around a 40% change in fuel economy.

__________________
Doug

1987 300TD x 3
2005 E320CDI