I started using Mobil 1 High Mileage, I think its a 10-30 (California), on my 94 850 turbo. The leak I had in the crankcase went away shortly after and hasn't returned, and what I have read this is fairly common side affect of the seal conditioners in that oil. I also only change the oil at 5000m, t...

Look for vacuum leaks using WD40 or other flammable spray on hoses and intake manifold gasket areas. Minor leaks are noticed as rough idle and clear as throttle is opened. Don't start a fire! Old vacuum hoses are prime suspects. Hard plastic flex intake tubes are next suspect. volvolugnut Thank you...