GM 6.0L L96 at 66k; various 30 grade oils - AMS SIG, OE, Napa SYN

I like seeing TBN, but it costs extra (at least with Blackstone) and IMO not very useful unless the OCI is >5000 miles. I would never complain at or guilt someone into spending extra money on something that is not useful to them just because *I* want to see it.
There are others that don't charge extra for it, and its good to encourage people to use those since it provides a higher return for what they are paying. It doesn't make sense to not try and get one of the others that come with it. Otherwise you are just getting glimpses, checking for blue-moon problems. UOAs are primarily for reporting on the condition of the oil. A lot of people misapply UOAs or substitute them for other more appropriate, conclusive evaluations.
Last edited:
I would say of the three, the Napa is the best value for a 5500K OCI, but if you want to go further, the Amsoil Signature had double the TBN, maybe could make 10K miles with decent numbers.
True. Only the OP’s engine, his driving habits, his oil of choice, and OAs can determine if the oil is suitable for his preferred OCI.
I drive hard, idle quite a bit, and basically max out the gvwr of my truck 50% of the time. I would say that my driving is severe. I suppose one thing is that the test engine is an LS based 6.0, which are classic for long term builds.......not really known for wearing out. Agreed that my report is for me, and not conclusive or indicative of anyone elses...........hell, could have broken a connecting rod, and punverized it into oblivion, the filter caught it all, and the test would still show good. I get it.
The Amsoil SS needs to be run longer. That is what it is made for. There is no advantage to running a long life oil and short intervals.running the oil at the lower miles. All of the oils did a great jpob at keeping the parts seperated.