Alright, you pro-cartridge filter guys make a convincing argument.
I knew this would devolve into an oil discussion thread. These kinds of threads always do.
Bob is the Oil Guy is a neat website. Lots of experienced wisdom there. I recall reading that even some Mobil 1 oils (not sure which weight) are now group III, not group IV.
I remember going UP the road to Big Bear Mountain really fast in a turbo MX-6 GT at night, popping the hood, and seeing the turbocharger
GLOWING ORANGE. It was so hot, it was emitting
visible light. Oil life has to be shortened in such high heat conditions.
To summarize, 15,000 mile oil change intervals on a turbocharged car is probably not a good idea if you plan on keeping the car long term.