HMMmmmmmm... do I sense another oil debate. I agree with Jim, that mechanic is blowing smoke. Castrol is good oil, it's Quakermistake, I mean Quakerstate and Pennzoil that you want to stay away from. That mechanic may be telling you to use Quakerstate because that's what his dealership sells. A lot of dealerships will recommend what ever oil they can get the best deal on, providing it meets MB standards. Now there is a difference between just meeting a standard and exceeding it. I mean, we all could live on bread and water, but what is best? I used Castrol GTX for years. I don't used it now because it doesn't have a "C" rating for my diesel.
1994 MB E320 Coupe (199,500 mi)
1992 MB 190E 2.6 (173,000 mi)
1983 Porsche 911SC (148,000 mi)
2004 Volvo V70 2.5T (198,000 mi)
President of CT/Westchester Section