I'm not trying to start an argument here, but I disagree here. I can't even begin to count how many times I see people at the field trying to "squeeze" a couple extra hundred RPM out of their engines, and then wind up with a lean run that burns up the engine. Because of this I will never buy a used engine unless I know the person selling it. If I know the person takes care of their engines and always run them rich I will buy, otherwise I buy a new engine. The little bit extra it costs is worth it to me for the piece of mind that I get from know my engine hasn't been abused and ruined. It only takes one or two lean runs to burn an engine in an aircraft.

Ken