I don't understand the multi grades. I have a 1932 model McCormick Deering tractor. When I got it, I changed the oil, and put a multi grade in it. (I think it was 10 / 30), and I had very little pressure. After thinking about it for a little, I decided I had made a mistake, took that out, and replaced it with 30 weight, non detergent. The pressure is now better, and holds up better after the engine gets hot.
I decided to use a non detergent, because I'm sure the engine is full of sludge, I don't want to take it apart, and I don't want all that crud breaking loose.
If the multi grades really are good from 20 to 50 for example, why are they so light and thin? It would seem that if they cover so many bases, they would get heavier as they get hotter. I know that doesn't happen, but why not? Allen
