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What does oil do in a car?

A mechanic checks the oil in an Audi.

Motor oil is critical to the functioning of vehicles equipped with internal combustion engines. Just as blood travels through the human body and brings oxygen and nutrients with it, oil travels through the engine, supplying lubrication to keep essential parts moving. Changing the oil on a regular basis is important, and neglecting to do so can bring forth catastrophic consequences.

So what does oil do in a car? Once you know the specifics, you’ll surely keep this maintenance task at the top of your list.

An Oil Overview

The first petroleum-based lubricant was developed in 1866 by Dr. John Ellis and was designed to lubricate steam engines. Through constant innovation, this became the motor oil that kept early race cars and mass-produced vehicles like the Ford Model T moving. Since then, motor oils have become so essential to vehicle operation that even the newest, most complex gas and diesel engines still rely on them.

Lubrication and Protection

Ford Engine BayEngine parts that seem to touch are often designed to glide on a thin film of oil. Because oil helps the pieces slide easily, it greatly reduces engine wear. Friction also means heat, which can be bad for mechanical parts over time. By lubricating the engine components, oil helps to keep things cool.

Oil also prevents harmful deposits from forming on engine components and catches and holds debris, which will then be caught by the oil filter. This filter should always be removed and replaced during regular oil changes. In engines equipped with variable valve timing, oil serves as a hydraulic fluid to keep critical parts moving.

Finally, motor oil also has an environmental component. Specifically, it helps protect the emissions system through such additives as detergents, dispersants and friction-control substances. As a result, emissions levels fall. Picking the right oil viscosity can help the oil flow more easily through the engine and reduce resistance for moving parts, improving fuel economy.

Doing It Better With Synthetic Motor Oil

Conventional motor oils help keep engines running, but synthetic oils do it better. Synthetic oils utilize a complex chemical development process that removes impurities from crude oil and controls specific molecules to supply enhanced performance and protection.

Notably, synthetic oil does a better job of managing oil breakdown, thwarting sludge accumulation and deposit buildup, reducing wear, and protecting against high temperatures. Modern engines with boosting technologies like turbochargers and superchargers typically require synthetic oil. Other engines can benefit from them too, as oil change intervals are extended when you choose a full synthetic over conventional oil.

Shoppers can also find synthetic blend and high-mileage oil options, each with their own formulation and additives to maximize engine performance.

Oil Change Intervals

Always consult your owner’s manual for the recommended oil change intervals for your vehicle. Usually, manufacturers offer two maintenance schedules based on your driving habits: normal and heavy. Because most vehicles are driven in heavy traffic over short distances, following a heavy usage schedule is typically the best choice.

The owner’s manual will also list the type of oil recommended for your car. The manufacturer will usually note the oil types based on the climate where you live or based on the season, if temperatures vary widely there.

Never Neglect Oil Changes

If you skip an oil change or are running low on oil, your engine will run less efficiently. Moreover, dirt and debris will build, the engine will run hotter, and parts will simply wear down faster. In the worst-case scenario, the friction of metal against metal will eventually cause the engine to seize, damaging or destroying it. That’s definitely something worth avoiding, so remember to keep an eye on your oil and take your service intervals seriously.

Check the oils, chemicals and fluids available on NAPA Online, or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on what oil does in a car, chat with an expert at your local NAPA AUTO PARTS store.

Photo courtesy of Pixabay.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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