Engine hours mean almost nothing. Engine conditon is determined by 3 things
1) How the engine is operated. That is did the owner allow it to warm up, perform proper runups and did not overheat or evercool it .
2) Regular use. Almost all private aircraft engines expire prematurely from inactivity induced corrosion. A rough guide is the logbook should show a consistant 1 hour per week which about the minimum use to keep the engine healthy.
3) Proper Maintainance. Regular oil changes (the less use the more the oil should be changed) and proper up keep of the baffles, exhaust and airfilter/carb heat box are essential for engine longevity.
An instructive example is the tale of two Lyc 0320's ( 2 C172's ) The first had an engine with 2000 hours in 4 years and a known operator and maintainer history. The second was a 300 hour engine overhauled 10 years ago with a unknown history. I recommended the first, the PPL went for the second and in 2 years has had to replace the camshaft (spalled) and 2 cylinders (corrosion pits) at almost $12,000.
The 2000 hour engine airplane now has 2200 hours and other than oil changes the owner has spent zero dollars ahead of the firewall.... and he paid $10,000 less for the airplane.
