FYI: I was reading an article on high performance flat tappet life today. They made the statement not to use Rotella diesel oil anymore as the ZDDP is low like most motor oils now.
I know a lot of old car owners swear by and use Rotella diesel oil, which I always did NOT recommend because of the higher level of detergents would negatively impact old motors with accumulated sludge. I think(memory) the "classic car" oil has around 4000 ppm or similar high level which according to my sources and SAE reports, is not necessary. After a certain amount to coat the metal, any additional is excess/wasted at oil change time, and it tends to volatilize(15%) in the engines with a breather vent.
I checked Shell site and they show 1200 ppm Zn in Rotellas. I found this independent chart which compares a bunch of brands.
https://www.speedwaymotors.com/the-toolbox/zddp-content-chart-high-zinc-oil-list-brand-breakdown/32479 ZDDP is only supposedly an issue with flat tappet motors as a wear issue but may have other benefits/drawbacks.
I think oil flow and a few other factors are just as/more important for cam/tappet wear. Some of the old motors had partial or no oil filtration so were prone to clogging up the channels/galleys and can lead to poor lubrication and premature wear and failures.
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