Question:

When drizzling oil into a cylinder to narrow down leakage during a compression test, does an increase in psi ALWAYS mean piston rings are going/bad? Or, is it at all possible that drizzled oil can ALSO help seal valves? For example, hot engine.. oily vapors etc. and splashy splashy result in valves being sealed as well..? Or, is this conversation not worth having, and it’s piston rings every. single.. time... I’d appreciate very experienced knowledge here. Of course, I plan to perform a leak down here shortly.. Thanks for the conversations.

 

The oil test is a rings test only. A vacuum test is performed if valves are suspect. If the vacuum gauge needle bounces around while the engine is running you have leaky intake valves. If you have steady vacuum but the oil test doesn't yield results you can suspect exhaust valves.

 

The oil in the cylinder is just to make sure you're not testing compression on a dry cylinder which would yield lower than normal results.