Originally Posted By: Trav
Thanks Shannow. Is there any downside to running SL with the CAT or emission system?
Trav, to put Shannow's response in another way, the SL-spec 0W30 in question has pretty much the exact same ZDDP levels that the SN-spec 0W40 or 5W40 equivalents would have (we're talking strictly ACEA Ax/Bx oils, NOT Cx oils). So really, there is no difference in "CAT harming" additive levels between the SL 30 grade and the SN 40 grade. This is because the API limits SN 20 and 30 grade oils in terms of allowable Phos levels, but does not limit SN 40 or 50 grade oils. So, an oil can have a lot of ZDDP and be called SN if it is 40/50 grade, but the exact same oil in a 30 grade cannot be called SN (must be SL).
So choose any ACEA A3/B4 rated oil with appropriate VW specs for the car in question and don't worry about the semantics behind the SL/SN ratings (where they largely do not have any relevance in this case).