Engine Compression Check Reference
Differential compression check interpretation guide for Continental and Lycoming aircraft engines. Understand what your readings mean.
⚠️ Reference Guide Only
This is a reference guide only. All compression check findings must be documented, interpreted by a certificated A&P mechanic, and addressed per the applicable engine manufacturer's maintenance manual and overhaul manual.
Engine Configuration
Cylinder Readings (X / 80)
Continental Service Standard
Continental specifies minimum 60/80 for continued service. Investigate any cylinder below 75/80.
Leakage Location Guide
Air leaking from exhaust pipe
Exhaust valve not seating; burned or bent valve likely
Air leaking from carburetor/intake
Intake valve not seating; bent or burnt valve
Air leaking from crankcase breather
Worn piston rings or cylinder wall
Air leaking from adjacent cylinder's exhaust
Cracked cylinder head or blown head gasket
Whistling from oil filler cap
Piston rings / cylinder wall wear
Interpretation Scale
Important Disclaimer
This tool is provided for educational and reference purposes only. Always verify all calculations against FAA-approved maintenance manuals, aircraft documentation, and applicable regulations. Never use web-based tools as the sole basis for airworthiness decisions.