Smoking engine ?

[Richard Farrant]

Originally Posted by Lynn Eades

Cummins Blue diesel oil because the diesel oil has more zinc that most petrol engine oils. The diesel oil is high detergent and might help to un gum your oil rings (which sounds like the problem to me?)
If not then a mono 30 grade oil high in zinc (important) The zinc has been largely removed from petrol engine oil for "enviromental" reasons.
Do some research to bolster your choice.

I would not recommend using a high detergent diesel oil in an engine of this age which is probably been running on the old style monograde with little or no detergent. You may think it will un-gum the rings, but worse than that it will release all the sediments in lower part of the engine and put them in circulating and hence cause damage to the bearings. I have been 55 years in the trade working on engines and would never use a high detergent oil in and old engine of unknown history. Just changing the oil will not get rid of the sediment.
If it had just been overhauled and clean inside, then a different matter.