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Compression test results... ?!

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Hey guys. Did a wet and dry compression test this afternoon. In general car still feels very powerful and I'm not eating any oil. Or if I am it's so minor I don't notice.

Presuming cylinder 1 is closest to the boot:

1: 129

2: 125

3: 120

4: 110

Test was done with engine fully warmed up, all plugs removed, cables grounded. Throttle was NOT wide open however. I just cranked the engine until the needle stopped moving (avg 10 cranks each).

Then wet test, oil cap full in each cylinder (<30ml)

1: 143

2: 143

3: 141

4: 132

So I'm not sure how to interpret this...does it mean my rings are worn? Or can I not trust the dry readings because my throttle wasn't wide open? The dry readings are within 10% of each other but some of the dry readings (cyl 3/4) are more than 10% away from spec which the manual says is 140psi. Thoughts??

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Hi Benjamin,


before drawing any conclusions I would redo the the compression test. A compression test should be done with a warm engine and the throttle fully open. Further more the wet test should be done with a couple of drops of oil and not a cup.

As for the cylinder numbering no. 1 is the most forward one and no. 4 is the most aft one, in general cylinder numbering is done towards the power output (flywheel) side, no.1 being the one furtherst from the flywheel.


Hope this helps,



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I would not be worried. About those readings

Why did you test it?

Oil use or blue smoke is the best sign of ring wear.

More useful to say that the compression is balanced which is most important.

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It is a little out, 110 vs 129 but % wise not too bad. No blue smoke no oil loss. Turbo bearing were illy rebuilt two years ago so the smoke from that is gone, it's really pretty clean. Given compression is a bit down but not much does that mean its probably doing 210hp not 215 hp type thing?

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