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

That should be fine, but anything lower than 5W shouldn't be used. The first oil change in the 83 I used some Castrol Syntec Truck 15w40, figured it should clean stuff out before going to a full synthetic.

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I think it's OK... just don't leave it in there very long. I'd change it by 5000 miles and go back to a quality synthetic like M-1 or Amsoil. Also, it is approved by MB as well:

http://www.whnet.com/4x4/oil.html

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Speaking of Catrol, has anyone used Castrol Elixor which is used quite extensively on the truck racing circuit in Germany. Seems to be a high performance diesel oil.

From what I have seen all synthetic oil weights have a "C" rating. It just when it comes to dino oil, only 15W-40 is rated for diesels.

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