Ok so you have no leaks that you can find or see... There is one of two possibilities that I can see here:
1) You do have a leak somewhere and just havent found it (my guess)
or
2) You have an oil scavenging issue with your motor which cause the oil to leak out through your exhaust. (an easy way to tell is have a friend sit on the side of the road and drive up and down the road to see if any kind of smoke comes out your exhaust on heavy accel or deccel)
I watched a porche 911 loose 3 qts of oil in one track session!!! we gave him a few bottle of oil and told him to take it to a dealer ASAP!
If I were you I would take it to the dealer and have them take a look at it... but dont let them do the work... just find out whats wrong
I hope this helps and welcome to the community
