Original owner, all maintenance and oil changes completed early (full sync). Started to run rough then quickly into metal grinding, turned off right away - result....#1 cylinder valve broke, damaging cylinder -- total engine loss at 61K miles. Out of warranty. GM offered 30% cost share but cost under "goodwill" warranty more than paying over the counter (and only 12K/12Mo engine warranty). What a load of BS -- way to stand behind the Hummer brand GM!