So what do you think is wrong?

["Marc Dexter" <mdex@royallepage.ca>]

Just thought I would see what everyone thinks the problem is with my car...
I have an idea and the car is going in to the dealer (thank god for
warranty) first thing in the morning, but I would appreciate any feedback
because I don't have the utmost faith in the "Monkey Boys" in the service
departments ability to diagnose the problem.... So here it is... I started
the car up (A4 1.8t) and after warming the car up the emissions control
check engine light came on.... After pulling off the road I did the usual
look under the hood, check fluids, see if anything is hanging loose, and
what did I find.... the car was also down on oil.... and that is strange
because the car hasn't used ANY oil since the first oil change.... the car
was down about 1/2L since my last fuel fill up.... so there it is.... the
car still pulls well, not that I pushed it in my limp home, sounds normal,
nothing seems to be hanging loose, no obvious leaks (that I can see in the
dark with a flashlight)....   any ideas or insight would be greatly
appreciated.... Thank you in advance.... Marc