Hi. I have a 2002 318i and she uses a crazy amount of oil. about 4 litres in 6200km. Has 143000km on the clock so can't understand why. There's also some blue smoke on pullaway but only when she's up to normal operating temperature. Was told that it's rings but I had a compression test done and it's fine....? Could this also just be Valve stem seals? Is there a a diagnostic which could confirm this?