What do folks recommend as part of a PPI? A leak down test, a compression test or both? I've talked to a couple mechanics and have gotten two different answers as far as which is more valuable. Thanks.

 

Do a compression test first. If the results are good there's no need for a leakdown test since there won't be much leakage. If comp is low or below normal, then do a leakdown test to determine where the leakage is coming from.

 

If you're curious how they're done, watch these videos:

 

This

 

+1

and compression test will tell you which cylinder(s) to focus on for the leak down

For leakdown, listen at the intake and exhaust to determine if leakage is on either of those valves. If not, issue may be rings.