Looking for some feedback. I would like to increase the MPG on my '99 E300TD.

Like the performance, however I think with the 5-Speed the performance would not suffer much if I changed the rear diff to a lower ratio. I spend a lot of time between 65 and 75 mph and would like to decrease the engine rpm.

Currently it has a 3:42:1 rear end. I'm thinking about a rear end from an E430, which uses a 2.82:1. Another option would be an E320 diff, which uses a 3.07:1.

The route I travel every day is very flat, plus I figure if I ever needed extra performance I could always drop it into 4th for a 1:1 transmission ratio. If you look at the old '86-'87 300TD's and the 190 2.5TD they all had a 2.65:1 ratio, so why not use that on a newer diesel?

Thanks for the inputs.