Cylinder-to-cylinder spread
Spread is calculated as (highest − lowest) ÷ highest × 100. This measures variation, not absolute engine health. Always compare against the manufacturer's limits.
Engine diagnostics, without the guesswork
Your cylinder readings.
Your engine's bigger picture.
Compare dry compression, wet-test changes, and leak-down percentages side by side. Record measurements worth investigating and print a useful worksheet.
No account requiredReadings stay on your deviceFree printable report
01 / Worksheet
Analyze your compression results
Example values are preloaded for demonstration—not real vehicle specifications.
▤ Test inputs EXAMPLE DATA
CylinderDry PSI *Wet PSI optionalLeak % optional
Only dry PSI readings are required. Leave optional fields blank if you didn't perform those tests. Test an engine according to its manufacturer's service procedure.
◉ Your analysis
Calculations run on your device. Saved worksheets use your browser's local storage, not an account or server.
02 / The method
Understand the measurements
Wet compression change
A higher wet reading can suggest changes in ring sealing, but it does not prove that piston rings—or any particular part—have failed.
Leak-down percentage
Measured leakage depends on the tester, engine position and pressure settings. Listen for leak location and compare under repeatable conditions.
Want the full procedures? Read the compression testing guide or leak-down testing guide.
03 / Common questions
Questions before you test
What is good compression PSI?
There is no universal PSI target. The correct minimum and maximum allowable variation depend on your specific engine and manufacturer procedure.
Is a 10% difference bad?
Not necessarily. Our default 10% threshold is only a configurable comparison and must never override your factory specification.
Does a wet test diagnose worn rings?
No. A noticeable rise may support further investigation of cylinder sealing but cannot definitively diagnose a specific component.
Should I use leak-down and compression tests together?
They answer different questions. Compression observes cranking pressure; leak-down checks sealing with externally supplied air. Combined results are often more informative.
Built to be useful, not noisy
One page. Clearer measurements.
Bookmark your free diagnostic worksheet for your next engine test.
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