Why do you suppose VW persists with the 40 weight oil specification (VW 502 00), when many competitors have been specifying 20 weight oils for many years with good engine longevity? Do passenger cars like the Passat and Jetta really need thick oil? For one thing, SAE 40 exacts a fuel efficiency penalty compared to SAE 20. VW must have spent a fortune redesigning their new gen-3 1.8T engine for improved efficiency (their stated goal), yet they seemingly shoot themselves in the foot by going with 40 weight. One would think the new engine would have been redesigned from the outset to work with 20 weight or at most 30 weight oil? My guess is that VW engines run hot (which is why they often come with oil coolers). So maybe 40 weight in a hot engine has the same viscosity as a cooler running Honda Civic engine with 20 weight oil? Just speculation, though. Or does VW assume we drive wide open on the Autobahn every day? Any thoughts on this?