Back sensor came on and taken the car to the garage to be told thats its a valve stem oil leak. comperssion is fine in all 4 cylinders but oil getting into the 4th cylinder. Upshot is that to fix, its c£600 as the head has to come off. Any pearls of wisdom or words to the wise on this. Car only done 60k. At present it has had an oil conditioner put into the system to re-elastocate the seals, however i suspect this is just a temporary win.! No smoke or miss-fire, care runs fine. Only just happened. How long will a treatment work before its requires mechanical input... not happy?????