Dear friends:

I've rummaged through my garage and found about 8 quarts of Castrol Syntec 5W-50 (API SL/CF) I bought a long time ago. Since most dino oils for diesel are 15W-40, I wonder whether 5W-50 is too thin for diesel (a 300SD)? I believe that Mobil Delvac 1 is 5W-40, so it seems that Castrol Syntec 5W-50 should be OK too. I wished I bought Castrol Syntec 20W-50 before.

What do you think? Anyone has used this oil/weight in their MB diesel?

Thanks.

Eric

P.S. I knew that Castrol Syntec is not true synthetic oil, but I bought it because Castrol USA was having some very good promotion at that time