[40 Deluxe]

[QUOTE=drolston;1941661]It is probably a really good product for old flatheads, with increased zinc for our flat tappet cams, and detergents to prevent sludge build up. But at $9.00 per quart, plus shipping, it is a little expensive. My solution is to use one quart of Valvoline TR1 racing oil for the zinc, and four quarts of any other good oil for the detergent and other additives.

Almost all modern oils still have some zinc, more than enough for a flathead (unless you have a top dollar race engine with extremely high valve spring pressure). Some of the very newest, like GF-6 or 7, may not be, but most oil ratings require backward compatibility. We don't want these newest oils anyway, because they have a viscosity rating in the range of 0W-16.
Any oil sold at Wal-Mart or anywhere else will work just fine in any street flathead, even one with a mild performance camshaft. I've noticed lately that non-detergent oils are labeled "not for use in engines" and are often labeled as "compressor oil".