Good for you. Mann filters are an excellent choice. Oil brand almost doesn't matter with modern oils if you are going to follow the severe service schedule. Any of the major name brand motor oils in the current SM rating are very good. Depending on where you live, Chevron Supreme or Texaco Havoline might be found on sale at bargain prices and they are a very well made oil.

If you have harsh winter conditions then I would run a synthetic at least for the winter.

Oil weight wise just follow the manual. My '96 850 manual suggested 15W-40 in the summer and 10W-30 the rest of the year, which is what I did.

I do not go for the long drain intervals Volvo claimed it's engines were ok for with conventional oils. My 850 manual said 10,000 miles. I said no way and followed the 5,000 mile severe service interval even though my driving didn't fit the severe service category. Never had oil leaks, plugged PCV system or the other problems one hears about and the inside of the oil cap area always looked clean. Last year I sold the car to a friend at 130,000 miles and they remain completely happy with the car.

John