A 1998 E320 should be an FSS type car, and there are a number of FSS equipped vehicles that were not maintained using Mobil 1, 15W-50 or 0W-40, that can suffer from oil related damage. The damage is a result of owners delaying oil changes until the FSS system told them it was time, when they did not use synthetic motor oils of the approved variety. The FSS system bases its intervals on using those Mobil products. Non-synthetic oils cannot support such extended change intervals.

Since the requirement to use Mobil 1 of the varieties noted was not clear in the manual, or apparently to the dealer service guys, Mercedes-Benz settled a class action court case by offering every FSS car an extended warranty against oil related failures for up to 150,000 miles. So, if you have an oil related failure and you have been using Mobil 1 since you got the car, you may be elligible for a free fix on MB, if there is a significant problem.

Good luck, Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)