You can think what you like, I know what I saw. I could actually see the oil leaking out from behind the harmonic resonator after I added mobile one. At the time I thought I was in serious trouble as that wasn't something that could be fixed cheaply. Although I haven't looked, but I believe there is no longer a leak after I topped up several times with castrol. Last top up was about 4 months ago. End of oil consumption suggests that. A taletell sign of a leak is the burning oil smell. I no longer have that. My own theory is that the mobile one oil has the wrong molecule size for BMW engines. It would leak where castrol would not.