What kind of oil shoud I use on this '31 motor. They guy I bought it from said it had been rebuilt and the valves hardened so it could burn modern fuel.
But I don't know if I should use a multi viscosity oil or straight 30. And how about detergent or non detergent.

Gotta31

If the engine was completely cleaned when it was rebuilt then a detergent oil should be fine.I like the multi viscosity oil as I feel it gets to lubricate the closer tolerance areas better,however this is just my personal opinion and I'm sure others will have varying opinions.You may want to do a search on this subject as it probably has been discussed previously.

Call the mfr. of the oil you will use.

Thanks, Guys.

Gotta31

i use exon oil designed for diesel engines in all my gasoline engines as the desiel oil still has adequate quantities of Zinc. mike

Modern 10W-30 has the best additive package and will be fine.Could also use straight detergent 30 in the summer or the 15W-40 truck oil that Mike mentioned.15W-40 could be a little "heavy" for a fresh engine.

I typically use 30W detergent in most of my early Chevys. That last one that I rebuilt got 10W-30. Felt that the 10 weight base would be better for break in. Likely will continue to use 10-30 in it. May change the others too as 30W is getting a little harder to find. For those in the frozen North 20W or 10W30 are your best options.