Sorry for the length of this but recently acquired a 2012 450i that had been rolled over. Was pretty beat and have straightened it out and replaced all of the parts that had been suspect. It starts right up and runs fine without power loss that I can tell, but it smokes when under load. I did a compression test which had good results, I have changed the oil several times due to the oil being milky gray which makes me suspect it was swamped. I have started to pull apart the top end to check things but to be honest not exactly sure what I am looking to see is amiss. I would assume with only 25 hours the rings are probably okay but is that a safe assumption? Oil is now clear, starts without issue and no error codes but still concerns me with the smoke without knowing exactly what is causing it. Anything I could check or advice from the top end perspective that may be a clue? I can inspect the rings but by sight not sure I would be able to tell if new rings would be the right move?

Take it to a dealer? Put it back together and run it for a few solid hours to see if it clears? Any advice appreciated. Thanks!

 

This may seem stupid but if the machine was rolled over and any oil collected in the exaust pipe you could simply be seeing that residual oil burning out when it gets hot enough. I would think that 25 hours is not enough time for the engine to have any major damage. I had the same issue with one of my honda's that got swamped and pushed all of the oil out and into the exhaust. I actually heated the pipe up with a torch to burn out the residual oil. Just my two cents from experience....