I understand the concern as many people feel the same way of synthetic vs conventional oil. I use synthetic motor oil in all of my cars and always have. Most of my cars are considered "older" and I have not experienced any leaking. I think when I buy my next car, I will use conventional oil and change more frequently, for example every 3000km/1850miles instead of 5000km/3000miles which will cost less and should be considered good maintenance.

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1989 300CE Astralsilber/Schwarz
1992 300CE Schwarz/Schwarz