A CPO is always nice because of the warranty. It is possible that the PO got the oil changed out of town. 10K for synthetic oil is normal these days because of the tighter tolerances in the engine and better viscosity of the oil. Also, the dealers are now starting to use synthetic instead of using 55 gallon drums of rot gut.

The synthetic in your S90 is keeping the engine cleaner than the old crud, keep using it! It will save your engine. I am surprised that the engine makes a difference in how it runs at the 3000 mark. It should still be good at 5000 miles between oil changes.

Even my diesel MB, which makes the oil BLACK in 1 hour of running, has an oil change every 12,000 miles or 1 year.

The Subaru is noisy, the technology is old, and the seats leave a lot to be desired. Their mpg is much better with the 4 banger, but don't try any 0-60 runs! Yes, the AWD is very good, but the sheet metal is quite thin. They do have a better resale value than most cars. But the Subaru is still just a car.

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Keeping it running is better than buying new