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3. You could be leaking oil through your turbo(s) and into the intake charge pipe that feeds the compressed air into the engine's intake manifold.
4. A faulty/leaking PCV system. T
In either case you'd see quite a lot of oil in your charge pipe. With #4, you'd see it pretty much past where the return PCV crankcase air was being re-introduced into the charge pipe, and not before that point. In #3, you'd see oil all that back up the charge pipe and towards the turbos themselves.
Sorry I was so late in replying--I didn't even see the message notification until just now....
Generally, burning a quart in a month (I assume something like 1k miles per month) is definitely not normal. And 70k miles is NOT high mileage. My '07 has 86k miles on it and doesn't burn oil like that.
A few possibilities, most of which require some diagnostic tests, with equipment.
A simple check though, is to make sure that you don't have oil in your coolant. Also the reverse. Coolant in oil makes it look milky.
This could be an indicator of a leaky or blown head gasket.
1. leaking valve guides in one or more combustion chambers.
2. loose/leaky compression rings on one or more cylinders.
In both cases, a variation of a cylinder leak-down test would show up the problem.
You could also pull the spark plugs out and see if any of them are oil-fouled.
Can you tell me of the issues with the '07 335i? Specifically, what do you know about burning a qt of oil in about a month's time? It's not even a daily driver. It's currently running Redline RW-30 as recommended by an indy mech upon telling him of the situation. He said it was burning oil like that because of the mileage (70K). It's also spitting a puff of white smoke from the exhausts when shifting gears at high speeds/revs, or downshifting to accelerate. What do you think?