How it is ensured that piston rings needs replacement?

Well, there are only two ways to really know if the piston rings need to be replaced. One is to check the oil and see if the engine is burning it. When an engine does burn oil, it means that all three rings (two compression rings and an oil ring) have a slight gap between the rings themselves and the cylinder wall. When that happens, it also means that there will be a loss in power, not much, but there will be some. The other way that I could think of is whether or not the engine has been abused in some way or another. I have heard of many ways an engine could be abused. I have even heard that my aunt had a 1966 Plymouth Fury with a 318, and she managed to have the block heated up to the point where

the engine was glowing red, yet the engine was completely usable after that for another two years, yet a neighbor of mine ran a truck with the same engine that you are asking about for about 11 miles when the engine had no oil in the pan from it rusting through. In reality, the best way to know if your engine needs new rings is if you take the engine apart and check the clearances. Otherwise, you can only guess.