SL-320 gas milage

[RConrad]

I have a 96 S-320 that gets 27mpg at 80 mph highway and a 97 SL-320 that only gets 23/24 mpg at 75 mph highway. Same engine, but noticed the S is only turning 26/2700 rpm at 80, while the SL is turning 3000 at 75/76 mph. Has anyone ever tried to change the rear on an SL to increase the milage. I'am not concerned with get-up and go as the mpg what with the price of fuel. Maybe the rear from an S would fit the SL??? Ron

[deanyel]

Sounds like it would probably work. I would first try to find out what axle ratio you have in each one. If you can't find it in print, it should be stamped on side of the rear axle. If that doesn't work you can jack up the rear end and count the revolutions of the rear wheels versus the axle. I would think a visit to a dealer parts guy would be productive as well. The replacement unit might be pricey as there aren't too many cars in the salvage yard yet. An SL500 is almost certainly a taller ratio (2.65 maybe?) and would likely fit - although you can't assume anything anymore. I would think you're looking at at least a day of labor. It's going to be a very long payback period in gas savings.