I authored an article in the current issue of Vintage Truck Magazine on this very topic. I spent a lot of time reseaching this and have quite a bit of technical data, interviews, and information to back up my article and I'm happy to share it with anyone who is interested.
In a nutshell, emmissions requirements have forced reductions of some key ingredients in gasoline engine oils that are vital to the life of flat tappet motors. There continues to be debate, both from viewpoints and from scientific fact, as to whether those reduced bi-metallic lubricant compounds will cause excessive wear in a broken-in engine as much as in a new rebuild. Spring pressures have something to do with it, but absolutely in no way are the exclusively the cause and problem so realize that there are many factors in play on this topic and facts are few and opinions are many.
I have plenty of facts from my research which includes the latest release of a technical bulletin from AERA (Automotive Engine Rebuilder's Association) on this topic.
Those advocating the use Delo, DelVac, and Rotella are in the right direction in MY OPINION, and factually, those diesel formulated engine oils available today contain zinc and phosphate levels that compare equally to the levels found gasoline engine oils 20 years ago.
GM has discontinued the production of and offering of their P/N 1052367, EOS - Engine Oil Supplement, which is recommended by the AERA. I have cleaned out the local GM dealer inventory in my town and have enough to last me until I'm done playing with inline engines I think.
On the future front, the 10 PPM particulate filter and new '07 ultra-low sulfur diesel fuels are spiralling us down into the abyss with these important additives in diesel engine oils and I fear that sooner, rather than later, our only remaining compliant (for what WE need) oils will not be available. I'm hoarding oils right now as I think this reduction is coming this year but the oil companies that I've contacted remain very tight lipped about their plans, their formulas, and the future as it relates to flat tappet engines.
Do your homework on this topic folks, it may cost you a cam and lifters which are hard to replace if you don't.
