380SEL gas mileage
 

Is there anything I could do to make my car use up less gas such as the car running rich or lean? What can I "tweak" in the engine to make her go on a diet?

Best thing one can do to increase fuel mileage is to change driving habits. Try driving a bit like "grandpa" around town, take off gently from stop lights/signs, build your speed slowly (it will likely PO the folks behind you too), but I bet you'll see an increase. Game I sometimes play is to try and not let the economy meter go more than halfway through it's stoke.

When on the highway, ease up to cruising speed. When using the cruise control, ease it back up to the set speed before re-engaging. I just did a 1K trip in the 560, averaged 18.5 mpg with my last tank at 20.21 mpg.

On top of that I also use Red Lines fuel treatment. I started using that in the 4.5 and have gained about a 10% increase in mileage. Granted, that's only about 1.2 mpg, but on the 4.5 that is significant.

lol Mike...guess what I drive it like a grandpa and beleive me people get pissed off!!:D