I've heard the Mobile 1 V-twin synthetic oil is also okay.
Seems the motorcycle and Diesel oils have more phosphorus and zinc additives.

Todd

 -------------- Original message ----------------------
From: Mike S <mikes@FLATSURFACE.COM>
> At 06:11 PM 9/13/2007, Todd Last wrote...
> >I thought you were not supposed to run SM rated oils because of the
> >lack of zinc additive?
>
> Shell Rotella T "Synthetic" (actually, a Group III, hydrocracked
> petroleum basestock) 15W-40 is available for fairly cheap at
> Wally-world (~$14/gallon). Although marketed as a diesel oil, it also
> carries an SL/SJ/SH (but not SM) rating. http://tinyurl.com/2ms42g
>
> VW approves a 15W-40 to the same max temp as a 20W-50, but you also
> pick up some extension on the low temp end.