En gine oil for 1944 Farmall H

Manual says to use 30W above 80F and 20W between 32F-80F. Suppose I should use 10W30, 10W40 or other? I had the oil pan and rocker cover off to clean the inside. I did not remove the head, pistons or crank but did replace crank seals, gaskets, etc.

Am sure you already know this but oil technology has greatly evolved since your manual was written. The additive package is much better in multi-viscoity oils. Engines that run their entire life on single viscosity oil (i.e. SAE 30) will have much more carbon in the ring pack area of the piston. This carbon is very hard and will contribute to wear (over a long period of time) of the piston rings, piston and liner.
Multi-viscosity oils also contribute to easier starting in cold temperatures.
I would recommend 10W30 or 10W40 if you operate at high load factors for extended periods of time at temperatures over 80 deg or so. It is not a big deal either way.

The only exception is the first fill of oil after a rebuild. All "break in" oil has a limited additive package allowing the rings to seat (or wear a little). Some engine companies recommend "break in" oil while others don't.

I would not use synthetic oil as a first fill after a rebuild as it will make it even more difficult for rings to seat due to superior lubricating qualities. It is up you but I don't think synthetic oil is worth the extra money for a vintage tractor.

Hope this helps,

Bill.

I will add an oil to the recommendations of 2cyl.
15 40 diesel oil is also just great in the elder gas tractors. Jim

Sorry I can not agree with you on the 30W or a muti weight oil of today. All oils have additives in them to keep carbon etc from being a problem they all meet API and a good number of other specifications. Now if you compared an oil made back in say 1935 and one made today ya that is true

So what do you use?

I use what I use and that is what I use. All depends on what I am using it in

I run 15W40 diesel oil year round in my 48 H

was there alot of sludge inside engine? like it had been run on non detergent oil?
some will argue but its been my experience that changing a engine over to detergent oil will loosen all those deposits and clog the oil pickup screen and the engine will begin using oil...may take awhile depending on use.
i agree with everybody that newer oils are much better,but not in a old engine thats run for years on non detergent oil...over haul it and run your favorite grade.