http://www.valvoline.com/downloads/2008-003a.pdf I mainly happened to notice this yesterday when looking for any information on how long Valvoline VR1 is recommended to be ran. It's about Zinc and flat-tappet wear. "Many hands-on car enthusiasts and engine experts believe the lower levels of zinc in SM engine oil is causing excessive wear in older style push-rod and flat tappet engines. This is despite the fact that all new engine oil classifications are intended to be backward compatible. This has resulted in the widely accepted belief that modern engine oil is not adequate to protect older engines." I trust Valvoline. I mean, they are a huge, multi-$$$$$$ company. They have some great products. They seem to do 'tests' to advertise with. But this sounded like something straight off Royal Purple. You would think that a company like Valvoline would do a real test, unless it came back with results that would not be beneficial in their advertising. They have a page about Zinc that is based off of hearsay. I just think that's odd considering the day and age we live in. This is the most information you can find on the web. It's killing me that there are no facts about zinc/flat tappet wear that I can find.