My mileage is also favorable on the car computer versus my calculation but not by the margin some people have seen. I am running 22.7 since I got the E550 4 months ago but based on actual mileage and duel consumption I am getting 21.6. Not too far off but with almost 22 mpg with a V8 I am quite happy with the results.

Those are great results with the V8. How long are your trips/commute? I am getting about 16.5 mpg but most of my driving is trips of 2-6 miles one way. The car is computing about 17-17.5 mpg so about 0.5-1 mpg optimistic depending on the tank.

I have about a 12 mile ride to work with 9 of those miles highway. It also included a long trip from Houston to Atlanta and with the cruise at 75 or 80 it got almost 26 mpg by my count but 26.9 according to the car computer.

I have logged over 16k miles and the dash is always about 1 mpg optimistic over the real measurement: http://www.fuelly.com/driver/gregtr/e350