The compression readings cited in this forum discussion—60, 65, 61, 60, 70, and 62 (out of 80, using the standard differential compression tester)—sit in a range that warrants attention but does not automatically indicate impending cylinder failure. The FAA's general guidance in Advisory Circular 43.13-1B treats readings below 60/80 as a trigger for further investigation via borescope inspection, since differential compression alone cannot distinguish between normal ring seating wear, valve leakage, or a developing crack. In this case, no borescope survey was performed, which is a notable gap in an otherwise "thorough" pre-buy. For a Continental IO-550 (the typical SR22 powerplant) at 1,100 hours against a 2,200-hour TBO—almost exactly the midpoint of the engine's rated life—these numbers are plausible for normal wear, but the absence of borescope data leaves open questions about valve condition, cylinder wall scoring, and piston ring health that compression alone cannot answer.
For pilots and owners evaluating a purchase, this scenario underscores why compression testing is only one data point in a proper pre-buy protocol, not a pass/fail gate by itself. A cylinder reading in the low 60s could stay stable for hundreds of hours or could be masking early valve leakage that shows up as a hissing sound through the intake or exhaust during the test—information only a borescope or a technician's trained ear during the compression check can reveal. Buyers relying on a "no issues noted" summary from a shop, even a reputable type-specific facility like a Cirrus Service Center, should insist on seeing the actual borescope images and oil analysis trends (particularly for iron, aluminum, and chrome/nickel content) rather than accepting a clean bill of health based on compression numbers alone. Oil consumption trends over the preceding annual inspections, along with spectrographic oil analysis history, often tell a more reliable story about ring and cylinder wear than a single differential compression snapshot taken on the day of the pre-buy.
This matters commercially as well as operationally. Cylinder replacement on a six-cylinder IO-550 can run well into five figures if multiple jugs need attention, and that cost exposure directly affects negotiating leverage on the purchase price. Buyers of high-performance singles like the SR22 are increasingly sophisticated about engine reserves and should factor a potential mid-TBO top overhaul into their cost-of-ownership models regardless of what today's compression check shows, since Continental and Lycoming powerplants alike can develop cylinder issues well before reaching TBO, particularly in aircraft with inconsistent flying patterns, extended ground time, or operation in humid climates that promote corrosion.
Broadly, this thread reflects a persistent tension in the piston GA resale market: the industry lacks a fully standardized, universally trusted pre-purchase inspection protocol, leaving buyers to rely on forums, personal mechanics, and secondary opinions to validate a shop's findings. As legacy piston fleets age and TBO extensions become more common through programs like Continental's and Lycoming's factory overhaul incentives, borescope inspection is increasingly viewed by knowledgeable buyers and mechanics as a non-negotiable component of any serious pre-buy, not an optional add-on. Aircraft transaction volume in the high-performance single and cabin-class piston segment has remained robust, and as values climb, the cost of a $200-300 borescope survey is trivial compared to the risk of inheriting a cylinder replacement bill or, worse, a valve failure in flight. Prospective buyers and brokers alike would be well served by treating differential compression numbers as a screening tool that mandates further investigation rather than a final verdict on engine health.