I had an oil analysis run on my 2005 GP when it had about 25k on the clock after waiting on the DIC to tell me to change the oil - total about 13,000 miles on that Mobil 1 synthetic oil. Oil analysis from Blackstone Labs indicated the oil was still good BUT the particulates in the oil was too high. This indicates that the oil filtering is the weak link in the engine, not the oil. So, I choose to run cheaper, name brand dino oil and change every 5,000 mainly to get a new filter in the loop. I can't get the benefit from extended intervals to compensate for the increased cost of the synthetic. Just my experience.
