Use Walmart 15W40 for my '53 since it has all the Zinc in it. Note this is a diesel oil and not for late model cars with Cat. converters. Use in all my 'OLD' cars ~~~~~ and cheap.

Thanks Richard, what is the significance of the zinc please ?
Regards, Brian.

http://blog.hemmings.com/index.php/2012/10/18/tech-101-zinc-in-oil-and-its-effects-on-older-engines/

You can use any name brand motor oil, and add ZDDP (zinc). The zinc additive costs about $10 for a single oil change size bottle. My machinist insisted that I add it to protect my newly rebuilt 232.

I have been using Castrol 10-40 in my 51 Pacemaker for 26 years and no additives and no problems.

Straight 30 weight.

I've used 10W40 and more recently 15W40 in my 1951 Pacemaker engine, which has traveled about 49,000 miles of mostly highway driving in the last ten years. I change the oil every 1000 to 1200 miles, and do not have to add any between changes. The oil pressure is still very good. The engine has about 112,000 miles on it. I have not used any additives.

As Zack says, "Straight 30 weight." It works for me as I have had no problems.