I have a lovely 2011 E70 X5 without an N55 engine in it currently. The original N55 is out because it spun its crank hub due to a shoddy repair before I owned the vehicle. Luckily I have a great looking replacement N55 sitting in the garage getting ready to go in. Before I pop the engine in I’m doing all the stuff one should. Valve cove gasket, oil filter housing gasket, oil cooler gasket, oil pan gasket, etc… since the oil pan is going to be off I’m going to replace the rod bearings, which brings me to my question.

I plan on running the engine stock or maybe at a later date a very modest stg 1 Tune (think +50bhp). I can’t settle on what replacement rod bearing shells are going to give me the most longevity in a daily driver. I’m considering:
OEM BMW, King, or ACL. Does anyone have any experience running any of these (other than OEM)? Reading some of Kings own documentation I’m lead to believe that for a DD OEM might be the best because of better “embedability” (the ability to let contaminants meld to the surface of the bearing and not screw things up) and that King and ACL are more track and racing oriented.

Has anyone here been down this road before? I would just like this engine to last as well as it can.

Lastly I’m not considering the surface treated OEM bearings because of their exorbitant price.


My replacement engine has 93K on it, and I’ll be posting pics of the bearing shells once I get them out.
Cheers!