Just a side thought. If you have a "sludged up" engine...i.e., infrequent oil changes causing sludge to build up, you could have what is often called stuck rings. Basically, the groove in the piston that holds each of the rings can build up sludge and cause the rings to not move feely.

A solution that can help (short of taking them apart and cleaning them)is to run a couple oil change cycles using a fully synthetic oil like Mobil1 (has high detergents) or what I would more opt for since it is cheaper, run it with a quart of Marvel Mystery Oil (contains wintergreen oil and additives) which can really clean out any sludge or buildup nicely. Change the oil with whatever brand and subsitute a quart of MMO and run 3K miles or so and see what happens to your compression numbers.