That's a real common scenario in many of these failures. Many believe when there's no dripping, and no burning (smoke out the tailpipe) , that it's often related to the PCV valve. PCV =Positive Crankcase Ventilation, it's part of the emissions control system, but if it gets stuck (open IIRC), it allows the oil to be kind of sucked out.
When the oil is lost through the PCV valve, it's not "burned" and not blowing smoke from the exhaust...it's getting sucked out in vapor form through the PCV. The oil is going into the injection plenum and being burned off moderately.
It's like a $4 part, available at any autp parts stores..
Because of this belief (not confirmed, but many think it's true), many of us replace our PCV valve every other oil change. I actually do it every time, since I think it might be cheap insurance.
Yet some owners have never changed their PCV after thousands and thousands of miles with no problems.
My '01 with 77k doesn't consume a drop until I hit the highway for about 8 hrs straight.
You can change it yourself, super easy...
Here's a "How-To" I did:
http://www.vehicross.info/forums/sho...7&postcount=13
THE OEM PCV IS THE RUST COLOR THING, RIGHT ABOVE CYLINDER #3 ON THE DRIVER'S SIDE. CAN SEE IT AFTER YOU REMOVE THE PLASTIC ENGINE COVER.
IF YOU HAVE A RUST COLORED ONE, IT'S "LIKELY" THE ORIGINAL ONE INSTALLED AT THE FACTORY.