No, you won't likely see a headgasket problem on the M112 motor. Aluminum head and block makes it a little easier to keep a good seal in place.

Overall, the C43 is mostly a W202 with some extra goodies. The reliability of the C43 should be about what you can expect from a C280. The C43 has beefed up suspension and brakes as well as various cosmetic differences. The engine is a modified M112, which has proven to be a fairly reliable engine. The transmission is, for the most part, the same (a 722.6 with an extra clutch disk in each of the multiple disk clutch packs).

There are always risks associated with buying a new car, but I would not think that a fairly well maintained car should be terribly more expensive to maintain that a C280 (unless it needs engine work, in which case I imagine the parts cost more). Find a good one and have an extensive pre-purchase inspection done.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record