My thoughts exactly ever since I started looking into this about four years
ago, which is why I just don't trust it. Castrol GTX even though sold under
it's original API spec only seems to contain half the zinc and phosphorus it
did originally. I've seen a letter purporting to be from Royal Purple
stating that RP XPR 10W40 has over 1500-1600 ppm of ZDDP and goes on to say
"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". It which point the whole thing degenerates into farce. What
was apparent when I was looking is that Diesel oils, if they had a petrol
API rating as well as a Diesel, contained more ZDDP than oils with only that
petrol rating, but that was also under review. In the UK I use Comma Sonic
which is to API SL but has .2% zinc and .19% phosphorus
http://www.commaoil.com/productsguide/file/367670c3e9a411571893883585a71863
PaulH.
----- Original Message -----
> Can someone explain how Valvolene's VR1 meets the (claimed) SN/SM/SL
> rating, yet contains the claimed 0.14/0.13 Zinc/Phosphorus? As far as
> I can see, any oil rated higher than SL MUST contain less than .12%
> Zinc and Phosphorus.
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