The MB warranty is 50,000 miles or 5 years and the Starmark is an option (on specific pre-owned cars) to buy when you buy the car from a dealer. Covers lots of things, almost bumper to bumper, for a very reasonable price, no third party involved. It can be bought out to 100,000 miles or three addtional years. I think it is about $700 per year of purchase of coverage. I've had them on both my cars and they were both worth it for peace of mind at the minimum. Sometimes they overlap, for example my 99' E300 Turbodiesel is still under warranty (barely) but I bought the Starmark to cover it out to 100,000 miles or 2005. I think there is also an option to extend the Manf warranty too but I'm not sure of those attributes. Hope this helps. I recalling this stuff off the top of my head so some specifics might be a little different but the concept between the two packages is right.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles