[Guest]

I know its a topic that will cause debate but I've been wondering what is the correct engine type mineral or syntethic and W-grade. Ive got a recently overhauled 340.

[dave-r]

I use a multi grade synthetic. But don't use a thin oil as used in modern European/Jap cars. Don't use anything lighter than a 15W-40W or your oil pressure may drop if the engine gets very hot.

I have found Castrol 'Magnetec' to be very good at protecting the engine when starting from cold although all synthetics do this to some degree. Castrol sell two versions of the Magnetec. Use the heavier of the two.

[spitfire9137]

Have you broke in the engine yet, from what I have read it is not a good idea to break in with a syntethic.

[dave-r]

Yeah Spitfire that is a good point. I always use a cheap mineral oil for initial break in. But only if I know for sure everything is well greased/oiled before that first fire-up. Then I give it 500 miles before changing to a better oil.

[Guest]

It was broken in by the previous owner and I haven't had any visual leakage of any kind. The previous owner was using Gulf racing oil (I cant remember now the grade) and I noticed that the oil level disappeared quite fast. I haven't had any problems with the oil pressure and the electric fan switches on at quite a low temperature.

[dave-r]

If it has loose forged pistons in the holes it could well use oil. Keep an eye on it though in case you have damaged or worn piston rings. You could always do a compression test and then put a bit of oil in the bore and repeat the test to see if compression improves a lot or not.