I've seen the oposite when helping a buddy of mine put rod and main bearings in his mom's minivan. It is a 05 Caravan with the 3.8. It just started to spin one of the rod bearings and thats why we were replacing them. Shes owned it since new and the first year she owned it, had a fuel injector stick open. It diluted the oil pretty bad and we think some damage was done back then. It started making noise at around 140,000miles. Anyways, when we had it apart, there was a lot of varnish in it and its had nothing but Valvoline Synpower 5w30 in it, changed every 5,000-7,000miles with lots of mixed driving. Maybe it wasn't the oils fault, might just be an inherent thing in the 3.8 itself, but it kinda turned me off from their oil.