Our V10 TDI needs 12 liters of expensive, esoteric low-ash synthetic oil. The last time the dealer changed the oil it was $230. The next time, I tried buying my own oil and taking it to an indie shop. Alas, the cost was about the same.
I'm going back to the dealer next time. It's expensive, but change intervals are long (10K miles), and using the dealer should insure that the correct oil is used.
BTW, our Egg is now WAAAY overdue for an oil change @ 14,000 miles (I know, shame on me). It has used less than 1/2 pint of oil in this period. I'm impressed!
Regards.
P.S.: Why would you want to use any oil change interval other that that specified by VW??? That interval is presumably established by engineers and controls warranty coverage!