Engine Oil for Farmall M

This question has probably been asked before but I couldn't find it in the archives.

What type of oil should be used in the crankcase of my Farmall M? I'm located in SC where the winters are relatively mild. Is 10W-30 okay?

10w-30 or {5w-30 winter} will work fine.

Just my humble opinion, but I would not use 5w-30. 10w-30, or 10w-40 is fine. 15w-40 is a good choice also.

Rusty, I been thinking about using 15W-40 diesel engine oil in my old letter series Farmalls. I've seen a couple of posts here on the forum with thoughts in that direction and also have had some discussions with local folks on the matter as well. I've heard that zinc or some other element which these older engines like has been removed from all the gasoline automotive oils. Up until this point I have always just used a straight weight oil like 20W or 30W as recommended in the owners manual. I would be interested in your thoughts on this matter. My email is open if you want to respond off the forum - thanks for your comments, Hal.

Letter series IH tractors are very forgiving with the oil used in them.In the 40's and 50's most guys used a straight 30wt year around.If corn picking lasted into the sub zero months they just dumped some kerosene in the oil to thin it.

You being in South Carolina, I suspect you should use SAE 30 year around.

I have a 54 International 300u and I have used 15-40 Rotella diesel oil for last 10 years. I run it hard on a 6 ft bush hog and 2-16 plow. I used to run straight 30 detergent, but I was using 2 qts every 4 hours. With the Rotella 15-40, the 300U does not use any oil and runs execellent.

I am certainly NOT an oil expert and will never claim to be. Having said that, I did just recently start using the 15w-40 in one of my Hs. I based my decision on the fact that if the oil is good enough for a diesel engine, then it should be just fine in a gas burner, and I also found out that you can just about always find the 15w-40 is on sale somewhere and will actually be less expensive than what you would use in your car. Also, the H in question has always smoked a bit at start-up and then cleared up some but never went completely away, and with the 15w-40 the exhaust is now clean.

The compound is ZDDP. Oil companies started adding ZDDP (zinc dialkyldithiophosphate) to engine oil back in the 1950s to help reduce wear and tear during engine start-up. Test show on flat tappet cams it reduces bearing and journal wear by a factor of 20. It's that important.
This does not matter on Newer vehicles because most use a roller valvetrain.
According to the EPA and automakers, ZDDP deposits can damage catalytic converters in new cars, reducing their effectiveness as pollution control devices. The zinc bonds to the metal catalyst beads inside the converter, which undermines their purpose. For motor vehicles with catalytic converters (1975-up), it can mean increasing pollution levels from contaminated catalytic converters.

This is especially important when you first break in a flat tappet cam. I have personally seen 6 cars have the cam get wiped withen 500 miles do to the lack ZDDP. "Diesel" oil has more ZDDP than conventional oil. I cannot remembet the numbers off the top of my head , but IIRC the old stuff had 1500ppm, shell Rotella has 11 to 1200 and conventional oils had 5 or 6 hundred. I run A ZDDP adder on ALL of my old gas vehicle as well as rotella 15 40.

(quoted from post at 15:31:56 11/09/09) Rusty, I been thinking about using 15W-40 diesel engine oil in my old letter series Farmalls. I've seen a couple of posts here on the forum with thoughts in that direction and also have had some discussions with local folks on the matter as well. I've heard that zinc or some other element which these older engines like has been removed from all the gasoline automotive oils. Up until this point I have always just used a straight weight oil like 20W or 30W as recommended in the owners manual. I would be interested in your thoughts on this matter. My email is open if you want to respond off the forum - thanks for your comments, Hal.

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Hal, when I first researched oil, time and time again YT members told me that the zinc in the 15w-40 was what these old engines needed. So that's what I put in my H.