<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<HTML><HEAD>
<META content="text/html; charset=utf-8" http-equiv=Content-Type>
<META name=GENERATOR content="MSHTML 8.00.6001.23588">
<STYLE></STYLE>
</HEAD>
<BODY
style="WORD-WRAP: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space"
bgColor=#ffffff>
<DIV><FONT size=2>From my reading of spec sheets of oil available to me in the
UK modern oils (including for Diesel) have had their ZDDP reduced over time
as much for environmental reasons as for damage to catalysts, but then so have
some 'classic' 20W/50 formulations. ZDDP content is what the manufacturer
chooses to put in, so you can't say that any weight or API rating is
automatically going to have a particular content. For example a few years
ago Castrol XL 20W/50 SE was showing 800ppm, whereas GTX 15W/40
SL showed 1035, and GTX Diesel 15W/40 1200. For classics they
recommended their Syntec 20W/50 at 1200, whereas claims elsewhere said that
their GTX 20W/50 would always be 1300-140ppm. Mobil 1 Fuel Economy 0W/30
quoted 1000 whereas their Super 3000 Formula R 5W/30 showed 500. I've also
seen a letter purporting to be a letter from Royal Purple stating that RP XPR
10W40 has over 1500-1600 ppm of ZDDP and "we could take all of the ZDDP out of
our engine oils and still have 4 times the wear resistance of even the VR-1 oil
due to our Synerlec additive technology".</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>At the moment over here the highest concentration seems to be
Classic Oils Heritage 20W/50 at 1300ppm <A
href="https://www.classic-oils.net/Classic-Oils-Heritage-20W50">https://www.classic-oils.net/Classic-Oils-Heritage-20W50</A></FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>A friend has personal experience of a new cam and tappets
being wrecked in just 20k on a semi-synthetic 15W/40 SL, but from other things I
have read really old classifications such as SB never had that much to begin
with, and engines didn't suffer damage. So I suspect the problem with
rebuilt engines is as much to do with poorer quality components these days
as anything else.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>But as I say that's the situation over here, and as someone
else said this discussion could go on for ever.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>PaulH.</FONT></DIV></BODY></HTML>