Piston rings must deal with an assortment of issues.
Bad gas (detonation and pinging), dirty air and fuel, and contaminated oil all reduce the life of piston rings.
Maintaining the filters on your engine and regular oil changes make a big difference in how long the piston rings last. Once the rings have worn down, their ability to seal the combustion gases will become apparent.
The first sign of worn piston rings is blowby.
This will usually be seen through the tailpipe. Puffs of blue smoke out the exhaust means the engine is burning oil. You may notice that the engine oil gets low faster than before. Oil smoking first appears during engine cold starts. As the engine warms up, the pistons and rings expand, sealing the walls, reducing how much oil is blowing past the rings. Eventually, the rings wear to the point that there is constant blow-by, and the car smokes all the time. This can also be due to worn valve seals as well.
Another issue with blow-by is combustion gases entering the crankcase. This means fuel and combustion byproducts in the oil. As these chemicals permeate the oil, the oil loses its viscosity and the ability to cool and lubricate the engine. You must change the oil more often to keep the engine clean.
Eventually, the wear gets so bad that there is a loss of power, too much of the combustion gasses are being lost to the crankcase and too much oil is getting into the combustion chamber. This leads to fouled spark plugs and a poorly running engine.
The Top Compression Ring must deliver consistent compression sealing to maximize power output and control “blow-by”, gases which leak past the top ring. The Second Compression Ring, referred to as a compression ring, is actually a scraper which removes oil from the cylinder wall and keeps it out of the combustion chamber. The third, or Oil Ring, consists of an expander ring and two rails which control oil by drawing it off the cylinder walls and returning it to the crankcase via small drain-back slots in the rear wall of the oil ring grooves.