sooner4x4 wrote:
The assumption here is that dino oil needs to be changed out at 3000 miles. This Oil change interval is not necessary. A good quality dino oil can easily go 5000 or 6000 miles before needing to be changed. Nissan says it can go 7500 miles.
But everyone is free to do whatever they want and spend (waste) money as they see fit.
There are a variety of factors that will determine when the oil really needs to be changed. Things such as engine temperature, engine speed, crankcase pressure, and, as you mentioned, the quality of the oil.
But then again, oil is oil... it hasn't changed at all between 5000 years ago and now, so there's very little that the refineries can do to improve upon what they were bottling 50 years ago vs yesterday. Sure, they can add detergents and other additives to get the consumer to buy the more expensive units on the store shelves, but those don't protect the raw oil from breaking down at a much later time.
I absolutely agree that oil can go longer, as I typically have changed my dino oil between 4000 to 7000 miles. But I make my decision based upon how the vehicle is driven. I used to do mostly highway driving for my daily commutes for both work and school 10 years ago, so I felt the oil didn't need to be changed as often (this was in a '79 Chrysler Cordoba with a hard 186,000 miles on it..before I bought it). Also did the same in an '88 Ford Escort (which was rear-ended and totaled out, thus leading to the Cordoba, in case anyone was curios or cares).
3,000 miles is merely the safety point (worst case scenario). If oil has come such a long way over the years, we'd all be completely aware of which additives/formulas really do extend the life of the oil and provide a longer safety point. There's only one vehicle company I know of that used to endorse higher mileage intervals, and that's BMW. Not sure if they still do so or if there are other manufacturers that document/endorse it, but they used to put some kind of sensor in the crankcase that would eventually illuminate a dash light telling the driver it was time to change the oil. I have a friend that consistently went 7000-8000 miles before that dash light came on in his 318i.