Just got my UOA report from Blackstone and it looks like the viscosity is the limiting factor in my quest for extended OCIs. Amsoil S2000 0W-30, 12,500 rural mail route miles(about 650 hours)on the oil at the time of sample, and the viscosity is 80.6 (@210 degreesF)
Wear metals aren't bad, about the same as on a 9000 mile OCI without the bypass filter. Still thinking of changing to S3000 HDD, but it looks like there is no way I'm going to get 25,000 miles between changes on this vehicle, even with the Amsoil dual remote bypass. So the question is: how does Amsoil HDD fair with thickening?