How do you check for bad piston rings?

Typically, and generally speaking, black smoke indicates excess fuel cunsumption while oil burning is usually a bluish grey smoke. here are two types of rings on most pistons: Compression rings and Oil rings.

Compression rings are easily checked by performing a thorough compression test. Any competent technician would be able to perform a wet/ dry compression test to check for ring condition.

Oil rings are more difficult to verify. One simple test is to head down a steep long hill allowing the engine to slow the car, letting off the gas) at the bottom of the hill, accelerate and check for a excess "puff" of bluish grey smoke. This is often a good indication of worn oil rings (as opposed to other causes of oil consumption).