Changing the oil in a 240D

[gatekey]

I just bought a very nice 1980 240D from the original owner. The previous owner always used Castrol 20W50 (nondiesel) and the engine is quite good at 159,000 miles. The owner's manual does not mention any special diesel oil, just SAE grade vs temp range. Should I go to diesel grade oils?

[pawoSD]

Diesel oils are often formulated for soot control, something not found in gasoline engine oils, this can cause excess soot buildup in the oil which can be abrasive and cause excess wear on the engine. I'd recommend switching to a heavier grade diesel rated oil, I personally use 15w40 Shell Rotella T every 3000 miles in both of our diesels. This is one of the best oils for these cars as it is meant to be run in a diesel and has soot-control agents and is formulated for the environment in a diesel. I'd highly recommend this.

[Palangi]

Oils have changed and evolved over the years. The Castrol 20W50 probably was diesel rated at the time the car was made. Nowdays the standard for conventional diesel oilis 15w40. Any brand of 15w40 is OK, as far as I have ever seen, all 15w40's are diesel rated.

Oils which are not diesel rated are not like "poison" for diesels, it's just that there are better oils available nowdays as compared to when the car was made.

[vahe]

The original engine on my 240D 77 lasted about 300K, mostly stop & go city driving, at the end it was smoking blue pretty bad, the oil used was Castrol 30 weight. I replaced the motor with a new one from the dealer and am using Chevron Delo 15/40, let us see how long this one will last. Oh, I do change the oil/filter somwhere between 2K & 3K miles.
I did not know that there was such a thing as diesel formulated oil, learned about it on internet.
If your engine is in a good shape with no oil consumption, I would go with one of these diesel rated oils.

Thanks
Vahe

[gatekey]

Thanks for the responses. They make sense to me and I will switch to the modern 15W-40 Shell. My last hobby car was a two stroke DKW where oil is a VERY big issue so I may be overly sensitive to the subject.