The Stovebolt Site Forums The Shop Area Engine Shop motor oil for a 235

My 51 3100 has a rebuilt 59 235 in it. The motor is clean inside (no built up crud).When I got it I drained the crankcase and put in off the shelf brand name 10-30w oil. Now that I have a few hours on it and am installing an oil filter I want to change the oil.I plan on changing it often.
My question is,is there any reason not to use good quality 10-30w motor oil in my motor? If there is, what would you recommend?
Growing up I was taught to use non-detergent 30w oil in an old motor but this motor has been rebuilt and most likely cleaned so I'm assuming that basic motor oil is proper.
Thanks---Jack

Jack,

You might have opened a can of worms.

In the late 60s, I was also told to use non-detergent oil in a 216 and a high-pressure 235. However, by the time the high-pressure 235s were introduced (1953/54), GM was recommending detergent multi-grade oil.

GM was also recommending detergent oils in earlier years, for hard-working engines.

Your 10-30w (10-30, 10W-30) oil is OK.

Agree, A good brand of 10/30 will be excellent in that engine. When you get that oil filter on it you won't be able to see the oil on the stick as it will be so clean.

Detergent oil was available in the early 40's. In 1942 the US Military had almost universally switched to it and requiring filters on almost all motor vehicle engines.

A good 20W or 30W oil is all you need.

I would run a 20W oil over a 30W. Your main concern is engine start up and cold viscosity.

There is no reason not to use a good quality 10-30w oil in your motor (or, any other modern multi-grade oil).

"20W" is not 20 weight...

I ran 10W-30 in my rebuilt high oil pressure 235 with hydraulic lifters. I had one lifter that would clack until it reached operating temperature. I switched to 5W-30 and the lifter started to act right at all times thereafter.

But that's how it appears in the manual

You always want to run the lightest weight oil you can because the oil does not reach its listed viscosity when cold. 30 weight (or ever 30W) oil much more viscous 'cold' then when at operating temp... and the few minutes its takes to get to operating temp is when all the wear takes place.

You will see lower gauge pressure with the lower viscosity oil on worn engines and using 30 weight or even 40 weight oil is not a fix, just a crutch to make the oil gauge 'look right'.

So it is 'wrong' to use 30 weight oil? No. Given the choice 20W or even straight 20 weight oil is preferred.

And when we ran straight weight oils, we changed them summer and winter. Now we use multigrades, and only change them when needed. I'd give it a go with the 10W30. A light 20W may thin out too much in hot weather.

I"ll bite

Winter? Or Weather?

It's Winter.

It's winter in the southern hemisphere right now.
Carl

A name brand 10W-30 is all you need and you should be fine.