Not meant to be a discussion on what's best but i thought it would be usefully for people to say what they use it might help when the question comes up.
last year used 15/40 mineral, engine was running too hot due to missing tin, removal of oil found it very black after 1500 miles, this year with all tin present i used 10/40 semi, found it cleaner after more miles but a bit more leaky i guess from being thinner? gonna go back to 15/40 mineral next year to compare.
For what its worth! I was taught that "oil is cheap, engines are expensive" that was 50 years ago...and is still relevant today. When my bus was new, in Africa in the mid 70's I made a point of using Texaco 30 grade as per the VW handbook, here the average temp. was 90 degrees a 90 % humidity I changed the oil at 2000 Km intervals. The Humidity, emulsifies with the oil creating a nasty acid mixture, leading to corrosion and engine failure. After a move to Dubai I operated the bus in summer temperatures of up to 120 degrees and 90% humidity again changing it at 2000 km intervals. I changed to Castrol 20/50 multigrade due to progress in oil technology. The engine was still in excellent condition after 13 years in these conditions.....never used any oil, when I laid the bus up here in the UK. Its run trouble free, 112, 000 miles. The bus is currently with a Restoration company, which will include a complete O/H of the engine, I am very interested to see what the internal condition is. Tony
My oil 20/50 is still reasonably clear after 1000 miles! So is the oil in my modern car. If your oil goes black quickly you are 1. driving a diesel, 2. have worn piston rings, or 3. your exhaust valve guides are shot.
15w40 Comes in 20l drum from local ag dealer Ran coolest on this in my old cross dresser so stuck with it. Will experement again with stig having the type 4 engine to see if its still best
