My latest addition to the family is a '95 C280 with 165,000 miles on it. Runs like a top, doesn't miss a lick. The owner's manual doesn't specify which oil to use in it. I use 20w50 synthetic in my old 190E 2.6 and have never had any problem (226,000 miles). Which one should I use in the C280? I have some 10w30 I had bought just before I traded my cadillac...can I use that or do I need to exchange it?