Well, not to point out the obvious, but you are either burning it or leaking it out. Oil just doesn't disappear.
I'd start by checking the crankcase/PVC system. Since you have a catch can, I'd double and triple check the installation. Make sure that it was installed properly.
Next, I'd do a compression / leakdown test.
If all checks out there, I'd be looking hard at the turbo. Just because you can't see smoke in the exhaust doesn't mean that it isn't there. Could only be happening on higher boost due to crankcase pressure or something like that...
I hate to also point out the obvious, but I used to think my XT leaked oil. Are you checking the oil after the engine sits for a long time? I was not leaving enough time to check the oil. If the XT is not left alone for the entire night, I find it pointless to check the oil level.