While I respect TJKJ for many reasons I think Ill chime in a little bit here. I have a TDI Jetta and a CRD KJ. I use Amsoil European Car formula and Amsoil filters. The main issue with letting a good synthetic go high miles is filtration. I have a bypass oil filter in my TDI. I change the oil every 15,000 miles. I change out my engine oil filter (cartridge type) every 2500 miles and my bypass every 10,000 miles. Ive been doing oil analysis for years and every 15000 miles the lab tells me Im good and I can go longer. I dont, because I dont really want to.
IF youre able to change your oil filters regularly (2500 to 3000 mi) and youre using a good synthetic you can let it go much longer. 10,000 to 20,000 miles isnt unheard of WITH proper filtration.
2005 KJ CRD Sport
Suncoast, Transco, Inmotion, Provent, SEGR, CAT2, HID's, Samco hoses, louvers, V6 airbox, Fumoto, 2.5" cat back no muffler