My car is a 1999 V6 Vienta with 176000+ks on the clock I recently switched over to Nulon 10/40 have not used any oil, have not experienced any problems other than the oil discoloring a bit more than usual, which I expected and is a consequence of the fully synthetic oil doing a better job. Suggest doing an early oil change after the first refill, just to keep things right. By the way the car had been using Castrol Magnetec semi synthetic until then, which I understand is used by many, if not most dealers. Oh and I my mechanic did run an engine flush through first. I've used the same Mechanic for the past 20 years. He's fully Qualified,knows what he is doing and agreed the swap would be fine.