When looking at an oil for this car I am looking for:1) Resistance to shear because this engine shears down even the best oils in a very short time. Notably shear resistant oils such as German Castrol, Amsoil, and Redline are sheared in this car. I haven't seen any oil that does not shear in this car, it is only a question of how much it shears (thins out).
I would look at real world performance in UOAs first to see how much oils sheared and High Temperature High Shear (HTHS) performance second. VW 502 requires HTHS of only 3.5 cP. Redline 5W40 is at 4.6 and 10W40 is 4.7 and several Amsoil oils are right up there as well.
I would look at good base stocks such as group V third. Redline and Biosyn are thought to have largely group 5 basetocks in the mix along with group IV. I am sure some of the Amsoil products do as well I just don't know which ones.
Interesting video that shows how hot a turbo can get running at 5k rpm. http://www.youtube.com/watch?v...lated
2) Resistance to fuel dilution - Renewable Lubricants Biosyn may be the best out there for this
3) Ability to provide antiwear protection to the flat tappet fuel pump follower/cam. Look for high levels of Zinc and Phosphorus (ZDDP) Biosyn, redline, shaeffers, amsoil, and Rotella synthetic are all good in this regard and there are probably others but those ones jump out at me. Note that a minimum of 1200 ppm zinc has often been recommended for flat tappet engines. Check out the zinc levels of most 502 oils, they aren't that high for the most part,.
4) Ability to clean. M1 seems to do excellent in this regard. Oils with high Ca levels such as Rotella, Biosyn, Shaeffers, Amsoil, Redline, do well also. Ester based oils such as biosyn and redline have been noted as cleaning well. Ability to clean is especially important if the owner has not yet bypassed the pcv or implemented a good catch can system. The reason is because no fuel reaches the intake valves to clean them on this direct injection engine, therefore the volatilized oil, traveling through the pcv system is the only agent to clean the valves (note that valves don't need the cleaning if the pcv is bypassed).
5) Noack volatility - you want low volatility. Especially if you have stock pcv system.
6) high TBN - You want high Total Base Number TBN