How the Engine Lubrication System Works

Engine oil serves a vital purpose: it lubricates, cleans, and cools the many moving parts in an engine as they cycle thousands of times every minute. It reduces wear on engine components and ensures everything works efficiently at controlled temperatures. Keeping fresh oil moving through the lubrication system reduces the need for repairs and makes your engine last longer.

Engines have dozens of moving parts, and they all need to be well lubricated to provide smooth, consistent performance. Oil travels between the following parts as it flows through your engine:

Oil pan: Also known as the sump, the oil pan is usually situated at the bottom of an engine. Serves as a reservoir for oil. It is where the oil collects when the engine is shut off. Most vehicles hold between four and eight quarts of oil in the pan.

Oil pump: The oil pump pressurizes the oil, pushing it through the engine and keeping the components continuously lubricated.

Pickup tube: Driven by the oil pump, this tube sucks up oil from the oil pan when the engine is turned on, sending it through the oil filter and throughout the engine.

Pressure relief valve: Regulates oil pressure for a consistent flow as load and engine speed changes.

Oil filter: Strains the oil to trap debris, dirt, metal particles, and other contaminants that can wear down and cause damage to engine components.

Spurt holes and galleries: Channels and holes that are drilled or cast into the engine block and its components to ensure oil is evenly distributed to all parts.

Types of sumps

Two types of sumps exist. The first is a wet sump, which is used in the majority of vehicles. In this system, the oil pan is located at the bottom of the engine. This design is practical for most vehicles because the pan is located close to where the oil is drawn from, and is relatively inexpensive to manufacture and repair.

The second type of sump is a dry sump, which is most often seen on high-performance vehicles. The oil pan is located elsewhere on the engine, specifically not at the bottom. This design allows the vehicle to sit lower to the ground, which lowers the center of gravity and improves handling. It also helps prevent oil starvation if the oil sloshes away from the pickup tube under high cornering loads.

What engine oil does

The purpose of oil is to clean, cool, and lubricate engine components. Oil coats moving parts so that when they touch, they slide instead of scrape. Imagine two metal pieces moving against each other. Without oil they would scratch, burr, and otherwise cause damage. With oil between them, the two pieces slide with very little friction.

Oil also cleans moving engine parts. The combustion process creates contaminants, and over time tiny metal particles can build up as components slide against each other. If the engine has a leak or isn’t perfectly sealed, water, dirt, and road debris can get into the engine too. Oil works to trap these contaminants, where they are then strained out by the oil filter as the oil cycles through the engine.

The spurt holes spray oil onto the undersides of the pistons, which creates a tighter seal against the cylinder walls by forming a very thin layer of fluid between the parts. This helps improve efficiency and power, as the fuel in the combustion chamber can burn more completely.

Another important purpose for oil is that it carries heat away from the components, extending their life and preventing engine overheating. Without oil, the components would scrape against each other with bare metal-on-metal contact, creating a lot of friction and heat.

Types of oil

Oils are either petroleum-based or synthetic (non-petroleum) chemical compounds. They are usually a blend of various chemicals, which includes hydrocarbons, polyinternal olefins and polyalphaolefins. Oil is measured by its viscosity, or thickness. An oil must be thick enough to lubricate the components while being thin enough to move through the galleries and between tight clearances. Ambient temperature impacts the viscosity of the oil, so it must be able to maintain efficient flow even in cold winter and hot summer temperatures.

The majority of vehicles use conventional, petroleum-based oil, but many cars (especially performance-oriented ones) are designed to work with synthetic. Switching between the two can cause problems if your engine isn’t designed for one or the other. You may find that your engine begins to burn oil, where it gets into the combustion chamber and burns off, often producing telltale blue smoke from the exhaust pipe.

Castrol synthetic oil provides certain advantages for your car. Castrol EDGE oil isn’t as reactive to differences in temperature and can promote fuel economy. It also reduces friction on engine parts compared to petroleum-based oil. Castrol GTX Magnatec synthetic oil can promote engine lifespan and reduce the need for maintenance. Castrol EDGE High Mileage is specifically designed to protect older engines and improve their performance.

Grading the oil

When you see a carton of oil, you will notice a set of numbers on the label. This number indicates the grade of the oil, which is important in determining which oil to use in your vehicle. The grading system is defined by the Society of Automotive Engineers, which is why you will sometimes see SAE on the oil carton.

The SAE designates two grades to the oil. One is for the viscosity at a low temperature, and the second grade is for the viscosity at a high temperature, typically average engine operating temperature. For example, you will see an oil designated as SAE 10W-40. The 10W tells you that the oil has a viscosity of 10 in cold temperatures and a viscosity of 40 at high temperatures.

The grading begins at zero and increases in increments of five to ten. For example, you will see oil grades of 0, 5, 10, 15, 20, 25, 30, 40, 50, or 60. After the numbers 0, 5, 10, 15, or 25, you will see the letter W, which means winter. The lower the number before the W, the better it flows at lower temperatures.

Multi-grade oil is common with vehicles today. This type of oil has special additives that allow the oil to function well at different temperatures. These additives are called viscosity index improvers. In practical terms, it means that vehicle owners no longer have to change out their oil every spring and fall to adapt to changing temperatures as it was once common to do.

Oil with additives

In addition to viscosity index improvers, some manufacturers include other additives to improve the performance of the oil. For instance, detergents may be added to help clean the engine. Other additives may help prevent corrosion or neutralize acidic byproducts.

Molybdenum disulfide additives have been used to reduce wear and friction and were popular until the 1970s. Many additives have not been proven to improve performance or reduce wear and have become less common in today’s motor oils. Many older vehicles will have a zinc additive that is needed for the oil considering that the engine used to run on leaded fuel.

When the lubrication system doesn’t work properly, it can cause serious damage to an engine. One of the most obvious issues is when an engine leaks oil. If the issue isn’t addressed, the vehicle could run out of oil, which would cause the engine to quickly become damaged and need expensive repairs or replacements.

The first step is determining where the oil is leaking. It may come from a damaged or leaking seal or a gasket. If it is the oil pan gasket, it can easily be replaced on most vehicles. A leak in the head gasket can cause permanent damage to a vehicle’s engine, and the entire head gasket will need to be replaced if it’s leaking. If your coolant has a light brown color, this is an indication that the problem is a blown head gasket and that oil is leaking into the coolant.

Another issue is the oil pressure light coming on. Low pressure can occur for various reasons. If the wrong type of oil is put in a vehicle, it can lower the pressure in the summer or winter. A clogged filter or a faulty oil pump will also reduce the oil pressure.

Maintaining your lubrication system

To keep your engine in proper working order, you need to maintain the lubrication system. This means changing the oil and filter as recommended in your owner’s manual, which is usually every 3,000 to 7,000 miles. You also must use only the grade of oil that is recommended by the manufacturer. If you notice any problems with your engine or an oil leak, you should have your car serviced with high-quality Castrol oil by mobile technician from YourMechanic right away.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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