The whole ZDDP thing seems to be getting a bit silly. We've spoken to may people about it and here are the comments of John Rowland of Fuchs Silkolene (when it comes to oil, if he doesn't know it, it isn't worth knowing)

This fuss over ‘zinc’ is similar to the ‘lead-free’ panic of the late 1990s. I attempted to calm everyone down regarding ‘lead’ with a series of ‘Bulletin of the Morgan 3-Wheeler Club’ articles (widely circulated!) which I hope had some effect. Anyway, I’ve had no trouble with lead-free in my (unmodified) engines, and neither has anybody else as far as I know; unfortunately far too many valuable engines were vandalised by the fitting of unnecessary valve seat inserts. I am now trying to do likewise and defuse the damp squib which is the ‘zinc’ controversy, hopefully before anybody starts vandalising again!

The attachments (and attachments to attachments!) explain it all several times over, but it is worth stressing one or two points:
1) When you look at a technical spec of an oil, there are the contents (often in ppm) of various elements quoted, such as phosphorus, sulphur, calcium, zinc, magnesium etc. These are measured by flame or plasma spectrographs which break down the very large, complex organic molecules containing these elements, so that the emission or absorption spectra of the elements can be detected. (When I use the words ‘organic’ and ‘elements’ I am using them in the correct, chemical sense!) THE PURE ELEMENTS DO NOT EXIST IN THE ACTUAL OIL; it is the complex oil-soluble molecules which do the anti-wear, detergency, antioxidant activity etc.
2) In oil, zinc is a component of an anti-wear/antioxidant compound, ZDDP, zinc dialkyl di-thio phosphate. It works because of the phosphate component (containing phosphorus) and the ‘thio’ (sulphur) component. The zinc has no effect on the engine; it just holds the ZDDP molecule together! (Rather amusing really; everybody’s worrying about the inert bit!)
3) So……if anybody suggests boosting zinc with zinc pellets or whatever, this will be utterly ineffective, and the pellets/gadget/magic zincerator should be inserted in the most sensitive orifice of the vendor. (Remember the moronic Broquet tin pellets which ‘prevented’ valve seat trouble during the ‘lead-free’ panic?!) In fact, the zinc in ZDDP is a pain. When ZDDP burns (in engines that use oil, and they all do, to a greater or lesser extent) the ZDDP decomposes to leave white zinc oxide, a refractory ceramic-like deposit that acts as a ‘glow plug’ and initiates pre-ignition. So, very high zinc oils are NOT a good idea….USA web-sites please note.
4) ZDDP is effective and cheap. It is possible to make a zinc-free engine oil with excellent anti-wear /antioxidant performance….at a price. They already exist, for piston aero engines, where high oil consumption leads to pre-ignition thanks to zinc oxide deposits. I’d be only too happy to use such an oil in my ’34 990cc Matchless V-twin…….but I will not have to! There will be oils with more than adequate ZDDP contents around for the next 50 years at least.

Yours sincerely, John Rowland (R & D Dept.)