Originally Posted by WilsonTheDog
Do oil analysis if you're worried about it but I change it every 5k-7k. I'm almost to 7k on my oil now and it looks brand new (which is really no indication of wear but still).
Analysis is great, but at $25, it's only another $15 to just change it
Seriously... Change intervals beyond 15k are possible with a proper bypass filtration system installed. The cost of the system, plus the cost of the UOA, on a truck that only takes a $4 filter and $30 worth of synthetic 5w30/0w20, it's not worth it.
It's getting to be worth it on a 10-quart Duramax or 12-quart Powerjoke, but it really is not truly economically advantageous unless you're talking about long-haul OTR trucks that carry 10 gallons of oil... and can then run 60k between changes.
Synthetic oil is good. It's freaking awesome. It has a lower cold pour point for better protection in cold weather. It has better film retention, which reduces wear during the first seconds of operation following a cold startup. It has better shear stability due to the reduced percentage of viscosity improvers that are needed to create a multigrade oil.
All of the above allow it to be used for extended change intervals... and that is what has been pushed by Mobil and Amsoil, because one $45 oil change every 15,000 miles compared to three $20 oil changes every 15,000 miles makes synthetic look cheaper.
But extended OCI is NOT, and never has been the primary benefit of synthetic.
I run synthetic and change at 5k.