Historically with my other cars I was happy with a quart every 2K and really happy with a quart every 3K although I don't know if I ever had a car that good. Now I am spolied with the M111 that doesn't burn any. We have come a long way since the Ford Model A which had a recommended complete engine overhaul every 1000 miles! However I understand your feelings. I don't have much faith that the dealers "prescription" will have much effect. I would be surprised if sludge built up assuming they were using synthetic all the time, and I think Mercedes switched to using synthetic in 2000. At least on the C series they did. Mine ran the first 2 years on regular oil with no ill effects that I know of. Some others did get sludge. I am curious if the 5W40 meets the MB 229.3/229.5 spec.

Mike

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra