I've been trying to establish which oil to use/buy. I work on a fair amount of tdi's mainly from the 99 to 06 range. Always been buying the oil from the dealer. 5/40 castrol syntec for 2003 and prev and 5/30 2004 and after. I'm considering Amzoil. price is right and I beleive they have a good product. I would buy it in bulk Plus it's a friend who's a dealer. Amzoil just came out with a new 5/30 which has the 504 507 spec. the 5/40 is 505 01 spec. If i was south of the border I'd probably have some more options... but shipping is prohibitive. Anyone have any advice?