My latest analysis had an unusual statement on it "Oxidation is not available due to the string interference of ester-based synthetic. Guess that explains some of the bizarre results I have had previously. At any rate it really settled down this time even in the winter, with fe-11, pb-0, cu-4 al-6, and tbn-6.8 Last time was first after I had my intake manifold replaced for a very slow leak and this time the NA is down to 5 finally. Visc is 11 and was over 15 last time with 6K miles. Gotta wonder if the techs go on occasional benders!