Had the head gasket changed at 158k, now at 163k. I did a UOA at 500 mi and another 1000 after HG. This one is a further 3500 mi. There is a steady decrease in wear metals and silicon, which is kind of interesting to see. Looking at PPM/1000 mi, this is the trend at the 500 mile, 1500 mile, and 5000 mi marks:
Al - 11.61 / 4.89 / 0.85
Ch - 29.01 / 5.87 / 1.14
Fe - 56.09 / 23.46 / 5.97
Si - 81.24 / 49.85 / 11.66
I'm also impressed that the viscosity hardly dropped from virgin -- 8.38 cSt to 8.26 over 3500 mi. You can also see how the additives get depleted with use (mostly Boron). I did a VOA of this oil before it went into the sump, which I'll attach below the UOA:
Al - 11.61 / 4.89 / 0.85
Ch - 29.01 / 5.87 / 1.14
Fe - 56.09 / 23.46 / 5.97
Si - 81.24 / 49.85 / 11.66
I'm also impressed that the viscosity hardly dropped from virgin -- 8.38 cSt to 8.26 over 3500 mi. You can also see how the additives get depleted with use (mostly Boron). I did a VOA of this oil before it went into the sump, which I'll attach below the UOA: