I think Amsoil makes some vey good products, and is well represented on this forum by the very knowledgeable and expert people who are know Amsoil products.
But, there are people in the Amsoil front lines who drove me away from the product years ago...people who would pepper every forum with Amoil sale pitches.
The Amsoil guy I know just changes every customer to Amsoil at 1 year/ 25,000 mile OCI's.
I spoke to him about Oil Analysis, and changing oil filters, bypass filters, and topping off during the 25,000.
I also asked about whether he had concerns about the high amount of dust, and Mag Chlor salt we have. Since we drive a lot on forest service roads during the summer and during hunting season, and there are many trips into the desert.
We also face tons of liquid Mag Chlor sprayed on the highways during the winter.
As far as I can tell, he has no interest or cancerns in these areas He does not do anything but switch people to Amsoil and tell them to come back in 365 days, or 25,000 miles.
And in a state like Colorado 25,000 miles in a year is not uncommon.
Driving up long mountain passes at wide open throttle for 10 minutes or longer 6 times in a day is also not uncommon. Nor is towing heavy loads up these passes.
My first thought talking to this guy is that the Amsoil will probably make it the 25,000 miles and he won't see engine failures.... but I would think that these engines may not last as long as they could.