I agree with Larry, what kills Gas engines is the cylinder fuel washdown. That used to be an everyday event with carbureted gas engines due to the lack of good control of the fuel to air ratio. That in turn is due to a primitive fuel system (carburetor) that is unable to cope with all of the various environmental factors it experiences (cold temp/wide open throttle, ect).

Remember, a gas engine must run pretty darn close to 14.7:1 air to fuel ratio. A Diesel runs all over the place, but never gets near stoichometery.

With today's computer controlled fuel injection systems, the air to fuel ratio is controlled more exactly. The only time you get into an excessively rich situation is when a sensor fails (like the temp sensor). In this case, the check engine light should come on.

One other thing: You normally worry about EXHAUST valves and burning, not intake valves. They are the ones exposed to the high temps. Diesels will have a lower exhaust temperature than an equivalent gas engine. That is due to the higher compression ratio and is a natural result of the Diesel being more thermodynamically efficient. If you extract more work from the burning fuel, you have less heat left in the exhaust. This makes it easier on the exhaust valves and turbo.

That being said, MB's hardly ever burn exhaust valves anyway. They are typically sodium filled (at least on the gas engines).

BTW: There are plenty of examples of well cared for gas engines that have high mileage on them. One of the Technicians that works for us has a Ford pickup he bought with 35k miles on it and now has 350k on it. He drives from radar site to radar site and really racks up the miles. Another guy, Mr. Jordan, bought a new '76 Chevy stepside pickup with an iron headed Chevy small block in it. He lives in Norman, OK and commutes to OKC. He has 500k on his ORIGINAL, NEVER OPENED engine. Of course, he cares for his pickup meticuously. The ONLY nonscheduled service he has ever needed is R-12 to R-134 service.

Sholin

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What else, '73 MB 280 SEL (Lt Blue)
Daily driver: '84 190D 2.2 5 spd.