I see it a little differently as a compression test is easy, quick and reassuring if the numbers are in spec. If they aren't, well then you have your findings to deal with. It's kind of a make or break point in your diagnostic algorithm, and takes less time than a tune up. When my compression number...

Agreed. Compression test is a good thing to do also. Can be done as part of the checking the spark plug process as the plugs are out anyway.

Neil.