EOS is back; for a while it could be found on ACDelco's site, but now it seems to be on the Goodwrench site. It's $11.32 from GMPartsDirect.com - check it out:
http://www.goodwrench.com/PartsAccessories/EngineCareProducts.jsp
http://www.gmpartsdirect.com/results.cfm...tnumber=1052367
Originally Posted By: Jaybird
But what evidence can you point to that there is a great need for ZDDP at any level?
Do we simply take the words of a marketeer (with a vested interest in answering to the benefit of his product line), or an anecdote or two from pals?
What sort of study can we read determining that there needs to be a high rate of ZDDP?
Studies such as this one tend to show this not to be the case:
https://shop.sae.org/technical/papers/952344
I gather from this paper that the benefit of higher ZDDP was attributed to the fact that higher rates increased the oils ability to withstand oxidative thickening, and not with it's prowess as an AW film.
And when we break in parts, such as a valve train, are we not depending more on the EP regime of lubrication, than that of the AW regime that the anti-oxidant ZDDP happens to provide?
The evidence I know of is purely empirical: flat tappet cams and lifters broken in with low-ZDDP oils tend to fail. There were other factors involved for a time (such as lifter quality), but it seems that those have been resolved. The people telling gearheads to use high-ZDDP oil to break in flat-tappet cams are the cam companies, who don't sell oil. Sure, they sell break-in concentrate, but they're NOT saying that you should use more of it or that it's more important to buy it; it seems they don't care how much break-in concentrate they sell as long as they don't have to keep replacing cams because they fail during break-in. So the marketeering argument is out the window.
I have not read the paper to which you refer, but I did read the abstract, and I also determined that it was published in 1995. Yes, 0.8% and 0.6% are lower ZDDP concentrations than I would like to run with a flat tappet cam, especially during break-in. However, considering that the article was written in 1995 and the test was conducted on fleet vehicles, I strongly doubt that the low-ZDDP oils were used to break in the engines, which is the time most critical to have lots of ZDDP in the oil. Also, these were almost certainly OEM production cams and lifters which have much lower lifts, and require much less spring pressure. That translates to less friction and less pressure, which require less AW and EP protection.
As far as lubrication regime, I'm not sure. Although flat tappet lifter rotate in their bores when operating properly, they still must be considered sliding friction, perhaps somewhat similar to hypoid gears. The contact area between a lifter and a cam lobe is very small, so the pressure there is very high. I cannot imagine how it is possible that any film of oil exists in that interface, so what can possibly protect the lobes and lifters but an AW film? And lest you continue to think ZDDP is just an antioxidant, ask any oil formulator what it is, an he'll tell you it's an AW agent and antioxidant, it's a synergist, and he might even say it's also an EP agent.
Maybe you're right: maybe there's an additive other than ZDDP which can provide the same protection as ZDDP at the same or lower concentrations... but so far, it doesn't seem that anyone has identified such an additive. To paraphrase someone from this board, possibly MolaKule, 'ZDDP isn't the holy grail, just cheap and effective.' Cheap and effective sound about as close to a holy grail as is possible in this universe.
