What are car engine rings? 

This blog post will answer the question, ‘What are car engine rings?’, and cover topics like layout of engine rings, process of combustion, maintenance of engine rings, and signs of a defective piston ring.

What are car engine rings? 

Car engine rings or piston rings act as a seal between the pistons’ sides and the combustion chamber’s cylinder walls. 

This helps to prevent the combustion gases produced under high pressure and temperature conditions from seeping in through the openings and into the oil sump.

Piston rings also help to check the oil consumption rates as they act as a barrier that does not allow oil to flow into the combustion chamber above the optimal limit. 

Layout of engine rings

The car engine piston rings are comprised of three sets of rings. These rings are placed in sequence around the piston and play a vital role to help the piston produce power during the combustion process.

The first and the second rings are known as the compression rings. Their role is to act as a tight seal between the piston edges and the cylinder wall. This helps to block the passage of the highly pressurized combustion gases into the oil sump below.

The piston gap is usually about 0.2mm or even less. The compression rings do not act like piston skirts, instead, they use a thin film of oil to run. The compression rings allow the heat from the piston to escape into the coolant present via the presence of water jackets.

The third ring is known as the oil ring. It mainly helps in brushing oil from the cylinder walls as the piston goes through its upward and downward strokes, and brings that oil back to the oil sump. 

The combustion chamber is almost always being sprayed with oil from either the apertures in the connecting rod or the cylinder. The oil control ring on the piston mainly works to eliminate any excess oil from the piston and maintain the optimum level necessary for combustion.

Process of combustion

  • The hot combustion gases that are produced at high pressure inside the combustion chambers are used as the driving force for the piston movements which in turn, helps drive the wheels.
  • The combustion cycle starts with the inlet valve permitting the entry of the air-fuel mixture into the cylinder.
  • The piston reacts to this by moving downwards followed by compressing the air-fuel mixture as it moves upwards.
  • The compressed air-fuel mixture is then ignited by the spark plugs.
  • This ignition is done at very high pressure and the impact makes the pistons move downwards to transfer that power to the crankshaft via the connecting rod.
  • As discussed earlier, only the lower end of the connecting rod moves in a circular motion while the upper end stays fixed and restricted to linear motion.
  • The power is then transferred to the crankshaft that further sends it to the car wheels via a transmission system and the driveshafts.

Maintenance of engine rings

The maintenance of pistons and their rings can be carried out as follows:

  • Firstly remove the piston and rod assemblies from the engine and separate the two
  • Remove the rings from the pistons using a special ring tool
  • Remove the carbon deposits and varnish carefully from piston surfaces
  • Clean the ring grooves with a clean-out tool
  • Examine the piston carefully for wear, scuffs, cracks, damaged skirts, and worn-out ring grooves
  • Check the piston diameter if it is the same as the original measurements
  • Check the fitting of the piston pins in the piston bushings
  • The piston rings need to be checked for tension, scratches, and wear
  • New rings should be installed depending on their condition
  • Piston rings must be fitted to the cylinder and ring grooves in position
  • Resizing collapsed or worn-out pistons are not recommended by automotive manufacturers as excessive resizing can weaken the pistons.

Signs of a defective engine ring

The following signs are indicative of a defective piston ring that must be replaced with immediate effect:

  • Excessive exhaust smoke in the colors of dark grey or blue signifies worn-out or defective piston rings that are causing oil to leak into the combustion chamber and form such smoke after burning
  • Fuel consumption automatically increases as a defective piston ring causes leaked fuel to burn in the combustion chamber, thus resulting in more frequent refilling
  • Defective piston rings mean improper combustion, which equates to less than optimal power being produced for the car. This results in low acceleration.
  • The intake is filled with an oily texture of the same dark grey or blue color, which signifies the piston rings are defective and this can be seen as a blowby due to positive pressure in the PCV valve.

Research shows the features and ways to use a piston ring compressor, which is a special tool used to compress the piston rings in the event of a piston reinstallation.


This blog post addressed the question, ‘What are car engine rings? ’.

We came across the layout of engine rings, and the process of combustion. Furthermore, the maintenance procedure for pistons and their rings, and the signs of a defective piston ring have also been discussed. Please feel free to comment on the content or ask any questions in the comments section below.

Frequently Asked Questions (FAQs): What are car engine rings? 

How much does it cost to replace an engine ring?

An estimate of the total replacement cost needed for a car engine piston ring is somewhere around 1500-5500$. Although, the cost of replacement is totally dependent on the labor costs and the quoting price of the company that is replacing the piston rings.

What causes piston rings to wear out?

The primary cause behind the wearing out of the piston rings is dirty air or debris that enters the combustion chamber through bad or old air filters.

Are piston rings expensive?

The base price estimate of a piston ring is around 100-120$, the expensive part lies in the labor and the intricacy of the job involving the piston rings.