Bear with me folks, this is a bit emotional. I put the 50/50 Amsoil and Pennzoil 15W-40's together last night. Other than the "brief" flings I had with Chevron and ST oils during the AutoRx cleaning my old 1985 Volvo turbo has had Amsoil of different viscosities for many many moons. The car has 248K miles. So throwing a blend of oils in is not only heresy, it's totally anti-Al and probably violates the Patriot act as well. The oil change was nominal. Took my sample of the 10K mile straight Amsoil 15W-40. I'll post my old 10K sample in a few days...(Is half a sample bottle enough....I only got it 1/2 full, for some strange brain fert reason) Filled one FL-1A with the Penns, the other with Amsoil. Total of 3 qts of each in. All seems well...no difference in engine noise. One scary thing: The oil pressure is WAY higher when cold.....we can assume the reasons. Pressure is about the same hot. One question: Should I give in and add LC to the mix???