Well back in the days of carb's their was an advantage. Most engines were tired at 100k miles and ready for the scrap yard well before 200k. Where as you can expect 300k-400k out of a similer vintage diesel say a 617 before having to open it up. These days modern injection is so good that any gas engine given proper maintenance should be good for 300k miles, usualy the car will fall apart before the engine gives up. Just look at the oil, after 3k miles in my moms Toyota still looks new! New cars burn clean.

As for MB gas engines yeah they should last as long as any of the diesels. MB knows how to build an engine, the M119 V8 for example is an amazing power plant. I don't think you could drive enough to actualy wear one out.

Compared to our old cars, fuel economy is excellent. A new E350 will get about the same mileage as my SDL, and the engine puts out twice the power in a car that weighs more.

Part of the reason you see more high mileage diesels is because the of the people who buy them. If you drive a lot the diesel option looks pretty good, so high mileage drivers tend to buy them.

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2006 CL500
2009 C300 4matic
1969 280SE
2023 Ram 1500
2007 Tiara 3200