For the 4 years (while we still had an extended bumper to bumper warranty in service) we have been dealing with my local dealer Harbor GMC in Portage Indiana about an oil usage problem on our 2006 Envoy Denali, we were told that we had to do a consumption test and see the usage so we had the oil changed, and ran the vehicle for a 1000 miles and came back and it was down almost a quart, they said it was within specifications, I told them while pulling a 1200 pound boat to Paris Tennessee and back (about 760 miles) it used almost 5 quarts of oil, again another consumption test and was told to keep track of oil usage if I again towed the boat, again a few months later same situation, called the dealer while I was on my way back home from Tennessee and was told to add the oil, I took pictures of the dip stick, the 4 quarts of oil to be added, the dipstick level after and when I got home took it again to the dealer and was told that they would talk to my extended warranty company, well they said I could have the motor taken apart to try and find the cause and if it was something like carbon on the valves I would be responsible for the cost of the repairs, so it was a chance thing and we could not afford thousands of dollars for the repairs if it was something not covered by my warranty... Now that we no longer have a warranty to cover the repairs we started having problems with the engine running rough, so we had the tune up done and still was having the problem, now we are told by the mechanic that the # 6 cylinder has no compression and it showed a misfire code... 2500 misfires... On that cylinder... He believes that it is the exhaust valves but can not tell for sure unless he does a engine tear down.... 123,000 miles, 23000 miles after I no longer have a warranty... And from what I have researched there are a lot of people that have had or are having this problem, come on 80,000 miles and oil usage like that was from carbon build up on a valve... Now what do I do... Feel like taking it and parking it on the busiest corner we have near our GMC dealer and putting signs all over it... About being careful with oil usage in the GMC... This just makes me sick and only 5,000.00 from being paid off... bought it on March 16, 2011.... So now what do I do....