http://www.mobiloil.com/USA-English/MotorOil/Oils/Mobil_1_15W-50_.aspx

Mobil now claims their 15w-50 is now engineered for older vehicles that
need more anti wear additives. It has a lot of ash (1.2%) to prevent ring
sticking and oil analysis is showing it be well over 1,200 PPM zinc. It
does appear to vary. Last sample for FUN BUS came in at almost 1,600. The
Mobil 1 0w-40 is also up there. This issue with the ZDDP and ash is that
it fouls the catalytic converters. The low ZDDP oils are still at 800 PPM
and .8% ash so they are not zinc free. I also do not believe these modern
oil cause engine failures. There are still modern engines that use flat
lifters. Many after market cams are made from low quality cast billets
with improper heat treat and that is why they often fail and these
failures were a problem 25 years ago.

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
Mike S
Sent: Thursday, April 03, 2008 6:46 PM
To: vanagon@GERRY.VANAGON.COM
Subject: Re: Zincless Oil

At 04:18 PM 4/3/2008, Bob Stevens wrote...
>If the container says SM on it, it's zincless; and must say SJ (?) to
>be safe?

It is not that simple. There is no limit on zinc in any of the grades.
There are limits on phosphorus, which limits the use of ZDDP (zinc
dialkyl dithio phosphate), which is the antiwear additive that people
are concerned about.

API SJ has a "non-critical" phosphorus limit of 1000 PPM (0.1%) for
0W-20, 5W-20, 0W-30, 5W-30, and 10W-30 weights. It must pass the wear
test of ASTM D 4485 Test Method Sequence VE.

API SL rated engine oils required minimum 800 PPM phosphorus (as part
of ZDDP), _or_ a pass on the wear test mentioned above. It has the same
"non-critical" phosphorus limit as SJ.

The API SM spec has a phosphorus limit of 800 PPM, for the grades given
above. Other weights have no limit on phosphorus (or zinc). All weights
require a minimum of 600 PPM.

None of the weights with a phosphorus (and consequently a ZDDP) limit
are suitable for a VW aircooled engine. For the weights which are
suitable, there is therefore no way to tell from the API grade how
much, or how little, ZDDP is present, except that SM requires a minimum
of 600 PPM (which is about 1/2 of what was typically found in the old,
"good," oils).

In short, without an oil analysis, you can't tell.