You don't mention whether your 850 is a turbo model or not. I have a 97 855 T-5 and experienced an oil leak right at the 100K point. After reading the Brickboard and researching possible causes I elected to replace the oil filler cap gasket that was hard as a rock and the turbo return line gaskets and o-ring. Fixed my problem;, although your problem might be completely different altogether. You can check outr Volvospeed.com and in the repair section of Bay 13 it has a few ideas on possible oil leaks. The entire bottom of my engine was covered in oil so it was difficult to detremine where it was coming from and the small amount of money ($10) and time (30 minutes) made all the difference for me. Good luck. dw