A flick through the product catalogue of any major piston ring manufacturer will reveal a bewildering spectrum of styles and finishes. This leaflet summarises the most common types of piston ring used in today’s engines and explains the rational behind the designs.

Every piston ring is designed with a particular purpose in mind, although their functions fall into two broad categories. Firstly, to effectively seal the combustion chamber in order to maintain pressure and optimise energy output; secondly, to control lubrication oil consumption for the smooth operation and extended service life of moving components. Sealing rings are known collectively as ‘compression rings’ and oil distribution rings as ‘oil control rings’. Some rings however, are designed to perform both roles and therefore do not fit neatly in to either of the other two categories.