My last Report with Amsoil 5w20 SS at 5000 Miles looked excellent and the TBN was at 4.6. I do not believe in long oil intervals, here is Why CARBON, now before I get the typical Hate speech about wasting money let me explain. To me, oil is cheap engines are expensive, I own my vehicles until the wheels fall off. I will run the Signature Series to 7500 miles but not a mile more. My Theory is this - A Happy Oil is a Clean Oil.