Vad,
Not sure what he ran at first when the car was new, GTX I think but for the last 3 years at least he first ran Amsoil S2K 0W-30, then the new 5W-40 Amsoil for the last year. Changed twice per
year.
The dealer would not say what the actual problem was and my
nephew "assumed" it was a sludge issue as he had heard the
rumors. The dealer did no diagnostics that I am aware of.
The problem was the oil light going on sensing low oil pressure.
There was plenty of oil in the engine and it appeared OK by
visual inspection I was told. They may have replaced the oil
pump but not sure.
He has the car back and has done an AutoRx on it and it seems
to be running fine. He is not real happy with the VW response
as it took some saber rattling to get them to fix it.
Craig