A teaspoon of brake fluid will also unstick rings. Leave it in for atleast over night, but a week would be better. I've used this trick a number of times. I just used it this spring and brought a cylinder back from 85psi to over 300. So it works. Make sure you crank the engine over with all the injectors out to blow out the fluid that may still be in the cylinder before you do another compression test.

Also adjust the valves, tight valve clearences cause low compression.

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