From a 2007 Subaru Forester 2.5 naturally aspirated with 162K. I ran the oil to 8050 miles not by choice. I was a bit derelict in getting it changed. I had the external infamous head gasket leak and both HGs were replaced at 125k. This was my first UOA after that work a few years ago. This run was 75% open highway. I continue to be astounded how the plain Jane Chevron Supreme dino performs so well. With a TBN of 2.4 and viscosity holding up, I think 10k is doable. I don't see any use for syn other than cold startability. Filter was a PureOne. My air filter probably has 100k on it, I just keep cleaning it by hand. Si remains low.