The Volvo 5 cylinder engine likes synthetic oil and premium gas.

Personally, I'd use 5/30 full synthetic. More expensive than dino but you only need to change it every 7-8k or so instead of 5k. What's the service interval recommendation anyway? Synthetic will actually last 1OK+, but your filter probably won't.

Also use premium gas only. Regular gas will wear out your valve seats prematurely. I made the mistake of using regular gas in my 850 for years before reading here that I should be using 91 octane or higher. Bad mistake! The car now uses a quart every 2k or so. When I bought it, the 850 used about a quart every 4k. I'm convinced that if I had always used premium it would still use only a quart every 4k as the motor still runs great otherwise at 250k!

Enjoy the "new to you" car!