In this blog post, we’ll discuss the types of piston rings and their function in your common automobile engine.

What Are the Types of Piston Rings and Their Function?

Typically, regular automobile engine pistons utilize three piston rings. The first two engine piston rings would be the top ring and the second ring. Both rings’ job is to be able to press tightly against the engine cylinder wall, thus creating a seal for the combustion chamber. By maintaining this seal in the combustion chamber, these piston rings keep combustion gases in and keep out the oil.

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The third ring, which is the oil piston ring, is designed to scrape away any motor oil that accumulates on the cylinder wall as it travels downward on the cylinder. The goal is to send back the motor oil into the engine oil sump. Note that a very thin film of motor oil is normal for lubricating the piston ring cylinder wall mating surfaces. It is typical for some of the oil to burn away during the combustion process. What is considered to be “normal oil consumption” will depend on the engine’s condition.

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The function of piston rings is to create a strong seal between the cylinder wall and the piston. This seal is designed to prevent the high pressure combustion gases from going into the engine oil sump. Additionally, the oil piston ring is designed to control motor oil consumption by not allowing an excess amount of engine oil from going into the combustion chamber and burning away. It is important that piston rings function efficiently so as to allow the engine to produce the maximum amount of power.

Three types of piston rings.

The three types of piston rings.

Piston Rings Can Deteriorate Without the Proper Care

What happens when properly functioning piston rings start to deteriorate? When piston rings start to wear away, this creates an unwanted space or gap to form between the cylinder wall and the piston ring face. Once this unwanted gap starts to appear, then unwanted gas blow by is caused and enters the engine oil sump, resulting in a loss of engine efficiency and power. The gap now has disrupted the perfectly designed process of the combustion gases driving the piston down the cylinder wall, and thus turning the crankshaft.

With this gap now present, the ring’s seal is unable to keep these high pressure gases where they belong, which is not in the engine oil sump.  Also, these blow by gases will start to contaminate the engine oil, leading to shortened motor oil life and weakening of the engine oil’s ability to perform at protecting critical engine parts.

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Another unfortunate scenario that can happen in causing piston rings to malfunction is what we call stuck piston rings. When temperatures become extreme in the combustion chamber, these gases can start to break down motor oil, forming unwanted carbon deposits along the piston ring grooves. Byproducts of the combustion of gasoline can also create such deposits.

When such detrimental deposits become too large, the piston rings will start to stick within the grooves instead of maintaining their proper position within the piston’s grooves. Similarly to worn piston rings, stuck piston rings also can create an unwanted gap or space to form between the cylinder wall and ring area. This results in unwanted oil consumption and blow by gases.

Engine piston.

This piston could use a good synthetic motor oil to keep it deposit-free.

Some other clues that piston rings are starting to wear or create unnecessary problems would be blue smoke appearing out of your tail pipe when starting up your engine during cold starts. Since the engine is cold and not warmed up, the rings have not had the opportunity to expand within the cylinder. Worn piston rings are causing excessive oil consumption, thus leading to the blue smoke. Once you know this is occurring due to oil consumption, one will need to check the oil level more frequently and add oil as required.

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Another unfortunate byproduct of stuck rings or worn piston rings can be a reduction in horsepower and difficulty in starting the engine. In a perfect world, when you turn the engine over for startup, the piston’s function is to compress the precise fuel-oil mixture prior to the combustion explosion. When piston rings start to wear too much, the important compressed fuel-air mixture can escape the combustion chamber, leading to a reduction in engine compression.

When this starts to occur, it becomes more difficult to start the engine. Ultimately, once this scenario starts to play out regularly, this constant reduction in compression robs your motor of peak efficiency and horsepower. Now that we’ve discussed the types of piston rings and their function, and  what can happen when bad things occur to them, let’s talk about prevention of such problems.

Diagram showing stuck piston rings and properly functioning piston rings.

How to Protect Piston Rings

An ounce of protection is worth a pound of cure is quite applicable when devising a strategy to prevent unnecessary stuck rings and worn piston rings. Being proactive in this area is critical to preserving and maintaining your motor’s peak power, efficiency, and extended life. The easiest and most effective strategy to reach this goal is to choose the absolute finest engine oil available for your vehicle.

Without question, the number 1 choice would be using a top-of-the-line, high-performance synthetic oil. A properly formulated synthetic engine oil is formulated and engineered to withstand the highest of temperatures, having the ability to reduce and minimize friction and wear. A high-performance synthetic motor oil will keep piston ring areas clean from deposits and unwanted wear.

To provide some specific direction, consider for example a 100% pure synthetic motor oil from AMSOIL. One particular engine oil of theirs is called Signature Series Synthetic Motor Oil. During a well known industry leading specification test, this synthetic motor oil provided 75% greater motor protection against loss of horsepower and wear. This reduction means that critical engine components such as cams and pistons will last longer. More specifically to this blog post concerning piston rings, AMSOIL‘s Signature Series Synthetic Motor Oil left piston rings 62% cleaner than is required by a top industry standard specification.

No matter the types of piston rings and their function, always remember that there are things you can do to keep piston rings functioning at peak efficiency. By using the best possible synthetic motor oil in your engine, you’ve given your motor the best chance in living a long, healthy life.

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AMSOIL Synthetic Motor Oil is created using a perfectly even molecular structure that requires less energy to circulate throughout an engine, thus reducing friction and improving fuel economy.