I have a VW 105BHP 1.9TDI PD with 460.000KM on the clock, have this car from new.
Always changed oil between 20.000km en 30.000km (driven 60.000KM/Year)
With VW 50501 and most of the time with VW 50700 5W30 oil.
Never had one problem with this engine, camshaft, turbo, injectors, everything is...