yeah those BMWs and such use extremly precise machine work, they use mobil one best oil ever made crap, the 15,000 miles is under absolute ideal conditions ie.. driving LA to NYC and back 3 or 4 times with out stopping for anything but gas, and they also have huge oil capacitys cuz it takes longer to contaminate 15 qts than it does 5 qts.

And on the oil testing junk, oil will not break down, only get contaminated with fuel, condensation, blow by soot, dust, pieces of FRAM filters...