Ahhh yes the mystery of the missing oil. I'm had to find out the hard way why this was happening. If I were you, I'd get a compression check donw on your engine. Most likely, one of the pistons rings are shot and it's letting oil pass through. I was driving around doing the exact same thing and when I got it checked out, it seems thatI was basically driving on three cylinders. Luckily for me, the car was still under warranty, so I had to have the block, cylinders and rings all replaced. It was basically a rebuilt engine that they gave me. Depending on how many clicks you have, you might be able to swing it the way that I did. The volvo manual states that the engine should have it's oil changes every 16,000 km's. Ic canada that is. Of course everyone knows that that's insane!!!! But I guess they did'nt tell the previous owner of mine that. They got it changes every 16000 kms at the dealer and they had the records to prove it. And when I started to have these problems, I took it to them . They said that it was because the oil changes were'nt done often enough. duhh. So I showed them the record and to make a long.... llong story short, I had to fight to get another engine in my car. $10,000 worth of work!!!!! crazy!!!! And my car still isn't the same......

Good luck dude. I hope this gives you some ideas!!

Kevin,
Toronto, CA