Are you sure you're oil loss isn't from an external leak?

If not it could be the typical M54 oil control ring issue, some say it's vacuum related from the CCV, some say it's carbon build up, personally I have yet to experience either (knock on wood).

I would inspect the CCV hoses for oil build up, if none is present I would remove your spark plugs and inspect the piston tops, you won't see much but you will see the texture, which will show smooth or coarse indicating carbon build up.

Controlled amounts of seafoam though the brake booster hose on a hot engine would likely yield results if carbon is your culprit. I've used it many of times to restore compression in engines that have carbon build on on valve backings and such.

I plan on seafoaming my X5 even though there's no oil loss, but there is a good amount of varnish and emulsified oil residue where the oil likes to pool/rest. Barb adapter, clear hose and some vise grips. Should take about 8-10 minutes to do about 1/2 a can.

I have no external oil leak, i.e., no oil stain on the concrete driveway.

I hope you absorbed more from my post than just if you have external oil leaks lol.