[elhigh]

The name of the site is ecomodder, not ecoshopper. The point is to get the best possible mileage from the ride you already have. Pushing a big Benz past 30mpg is damned good and very respectable, but I have to wonder: to make it do better will probably require adding some aerodynamic upgrades to the beast. A Benz is a pretty reserved, refined ride and not the kind of thing you want to go making outre alterations to it.

Subdued wheel skirts may not look bad - look at some older SL models for examples, just a bit of a lip that covers some of the uppermost opening. It may not contribute enough to be noticeable.

There is probably quite a bit of aero you can do underneath, or look at an additional air dam.

If you want to do significantly better than you have already done, you will have to change to a different car if massive vehicle alterations are off your Benz's menu. Finally, the savings you realize from switching to a different car will be compounded by not requiring premium fuel - a "free" 15% improvement above and beyond however much you save with a thriftier ride.