my santro club 03 cylinder No.04 spark plug failed twice in 100 KMs drive. third time an electrician on my way Installed plug adapter, and told me that the rings of cylinder No.04 has failed, and due to which oil spilled over the plug and cause it to fail. due to this spill of engine oil over plug the car didn't maintained itself switched ON in CNG during idling while okay in higher gears.
Now the question is why this happens to only one cylinder? and what other parts should have had damaged so far, what kind of overhaul is need for my car's engine. thank you very much.