What Does Oil do in a Car? | Definitive Engine Oil Guide

You’re driving down the road and the oil change reminder comes on in your car. You know this is a signal that it’s time to get your oil changed, but what exactly does this mean? What’s going on under the hood?

Changing the oil in a car is a fairly quick and easy procedure, and it’s essential to keeping your engine clean and running effectively. Over time, regular oil changes will help to remove contaminants that have built up and extend the life of your engine, so it’s a worthwhile investment that shouldn’t be overlooked.

Keep reading to learn more about motor oil, including what it does, how often you should change it, the different types of oil and more.

Key points:

• Motor oil — also known as engine oil — is essential for lubricating engine parts, reducing friction and keeping the engine clean and efficient. It has evolved from a simple mixture to modern synthetic oils that offer wear protection, maintain viscosity across temperatures, prevent acid buildup and clean and protect engine components.
• What is motor oil made of? The composition of motor oil includes 70% to 90% base oils derived from natural gas or crude oil and 10% to 30% additives such as detergents, friction modifiers, antioxidants and viscosity index improvers. Synthetic motor oils, created through a chemically engineered process, offer superior performance in extreme temperatures and have fewer impurities compared with conventional oils.
• Crucial for engine performance is oil viscosity, a measure of how easily oil flows at a specific temperature. Multi-grade motor oils are formulated to maintain consistent viscosity over a wide temperature range, protecting engine parts from wear. Regular oil - changes are necessary to prevent the breakdown of viscosity index improvers.
• Different types of motor oils include synthetic blends, high mileage and conventional motor oils, each designed to meet specific engine needs. Motor oil grades are determined by the Society of Automotive Engineers (SAE) and indicate the oil's performance at various temperatures, with multi-grade oils being suitable for a wide range of conditions.
• Regular oil changes are vital for removing contaminants, preventing deposits and sludge and ensuring engine efficiency and longevity. The frequency of oil changes depends on factors like vehicle age, driving conditions and oil type. Modern cars often have indicators for oil level and change timing, but consulting the vehicle's manual or a technician is recommended for specific recommendations.

What Does Oil Do in a Car?

Motor oil was historically a simple mixture of base oil and additives, according to Pennzoil, the official lubricants provider of Universal Technical Institute (UTI) and a leading brand in the industry. It was designed to lubricate engine parts, reduce friction, clean, cool and protect the engine.

Oil in a car helps maintain engine efficiency by acting as a lubricant. This reduces friction between moving parts and prevents wear and tear. It also helps prevent acid build-up by neutralizing harmful acids formed during combustion, which protects engine components from potential damage.

Additionally, oil cleans and protects turbos and modern engine components by suspending dirt and debris. Corrosion inhibitors present in the oil further safeguard the engine by forming a protective layer on metal surfaces, reducing the risk of rust and corrosion.

Why does a car need oil?

Why does a car need oil? A car needs oil primarily for lubrication, cooling, cleaning and protecting engine components. Engine oil reduces friction between moving parts, preventing wear and tear that could lead to costly damage.

By minimizing friction, oil helps maintain the smooth and efficient operation of the engine. Additionally, oil acts as a coolant, dissipating heat generated by the engine and preventing overheating. It also plays a crucial role in cleaning by carrying away dirt, debris and microscopic metal particles, which are then trapped in the oil filter.

Regular oil changes are essential for maintaining engine health and performance, as old or dirty oil loses its effectiveness and can lead to increased friction, overheating and buildup of harmful deposits.

Is Engine Oil the Same as Motor Oil?

You might have heard engine oil referred to as motor oil or vice versa. Both products are the same in the market and simply refer to any substance with a base oil that’s laced with additives (anti-wear additives, dispersants and detergents, to name a few).

Motor oil vs. engine oil

Motor oil and engine oil are terms often used interchangeably to describe the same essential lubricant designed for the optimal performance and longevity of an internal combustion engine.

Despite the different names, both motor oil and engine oil serve identical primary functions:

• Lubricating moving parts to reduce friction and wear
• Cooling the engine
• Cleaning by trapping contaminants
• Protecting engine components from corrosion and rust

There are various types of motor and engine oils, including conventional, synthetic and synthetic blends, each offering distinct benefits for different engine requirements.

Is engine oil the same as motor oil? Both motor oil and engine oil are essentially the same thing, with a similar function.

Oil Viscosity Explained

When talking about motor oil, you’ll often hear the term “viscosity” being used. Essentially, oil viscosity refers to how easily oil pours at a specific temperature. Thinner oils flow easier at lower temperatures and have a lower viscosity, whereas thicker oils have a higher viscosity.

In cold weather, thin oils reduce friction and help engines to start quicker. In higher temperatures, thick oils maintain oil pressure and film strength and support heavier loads.

The viscosity index measures oil’s ability to resist changes in viscosity as temperature changes. Most multi-grade motor oils are formulated with viscosity index improvers, which use polymer additives to help maintain consistent oil viscosity over a wide range of temperatures—protecting engine parts from wear.

An oil with a higher viscosity index number can better retain its viscosity over a broader temperature range. However, these viscosity index improvers will break down over time as the oil ages. Changing your oil regularly will help prevent this.

What Is Synthetic Oil?

Engine oil has changed significantly over time. When it was first introduced in the 1800s, manufacturers used their own fuel and lubrication techniques, which led to many inconsistencies. The usage of animal fat and vegetable oil evolved into the use of motor oil made from crude. Later came the invention of synthetic oil.

Synthetic motor oil is oil that has gone through a chemically engineered process. When compared with conventional oil molecules, synthetic oil molecules are more uniform in shape and have fewer impurities. Typically, synthetic oil will have higher oxidation resistance and perform better in extreme high and low temperatures than conventional motor oil made from crude.

When fully formulated, motor oil is designed to serve a variety of different functions, including:

• Separating and lubricating moving parts
• Reducing engine wear
• Helping to prevent deposits from forming on internal engine components
• Removing and suspending dirt and contaminants in the oil until these contaminants can be removed at the next oil change
• Cooling engine parts
• Maintaining engine fuel efficiency and performance
• Providing protection across a wide range of temperatures.
• Functioning as hydraulics in variable valve timing
• Helping protect the emissions system

Is Synthetic Oil Made From Natural Gas Better?

Shell’s Pennzoil brand is known for creating the first synthetic motor oil made from natural gas. In the 1970s, Shell began investigating sources of energy other than crude oil, one of them being natural gas, to make fuel and lubricants.

The process of turning natural gas into oil is highly complex and has many stages, yet it offers superior benefits when compared with crude oil. Natural gas is very clean and free of many of the contaminants found in crude oil. When manufactured through their patented process, the result is a synthetic base oil that is purer and performs better than traditional base oils made from crude.

Thanks to the innovation and forward-thinking culture of Shell, the company was able to develop a full synthetic motor oil made from natural gas. This patented process is known as PurePlus Technology, which designs full synthetic motor oils that provide complete protection without compromise. Watch the video below to learn the details of how this process works:

Motor oil grades

Today’s motor oils are categorized based on a rating system developed by SAE, which rates oils by viscosity.

If you’re looking for an oil that can perform at a wide range of temperatures, you’ll want to opt for a multi-grade viscosity motor oil. An example of an SAE viscosity grade is 0W-20. The “0” symbolizes the cold temperature viscosity rating, the “W” stands for winter, and the 20 is the operating temperature viscosity rating.

As a rule of thumb, always look at your vehicle’s owner’s manual to determine the correct motor oil SAE grade for your specific engine.

Another symbol that commonly appears on motor oils is the API “donut.” API stands for the American Petroleum Institute, which offers a stamp of approval to help customers find engine oils that meet the minimum standards set by engine and vehicle manufacturers.

This symbol has three parts: the top half of the circle indicates the API service rating, the center of the circle displays the SAE viscosity and the lower half of the circle tells you the oil’s energy-conserving properties.

In addition to this, the ILSAC “starburst” can also be found on the motor oil bottle. This symbol appears on engine oils recommended for gasoline engines that have met API and certain fuel economy tests—the requirements of the International Lubricant Standardization and Approval Committee (ILSAC).

ILSAC GF-6 requirements

The GF-6 is the newest set of lubricant specifications set forth by the ILSAC that are designed to meet the demands of modern engine technology. This next-generation standard for passenger car motor oils calls for an expanded set of harsher testing related to wear protection, oxidation, fuel economy, sludge and protection from low-speed pre-ignition (LSPI).

So why was this development put in place? The ongoing push for greater fuel economy has resulted in engine downsizing that has grown the application of turbocharged gasoline direct injection (TGDI) engines. These engines require higher protection mentioned previously, including protection against LSPI and timing chain wear.

Introduced in 2020, the GF-6 provides improved protection and better fuel economy and helps reduce emissions for modern engines. Pennzoil motor oils have met these requirements for API SP and ILSAC GF-6, which can be seen on the packaging. To learn more about these exciting updates, visit Pennzoil’s website.

Other Types of Motor Oil

In addition to synthetic motor oil, there are three other common varieties of motor oil:

• Synthetic Blend Motor Oil: This type of oil uses a mixture of synthetic and conventional base oils to provide higher resistance to oxidation and better performance in low temperatures.
• High-Mileage Motor Oil: Formulated with unique additives, high-mileage motor oil helps to reduce oil burn-off and prevent oil leaks that can occur in older engines. This oil is designed for newer or late model vehicles with more than 75,000 miles.
• Conventional Motor Oil: Lastly, conventional motor oil comes in a variety of viscosity grades and quality levels. It meets the basic API specs recommended by your engine manufacturer but does not have the added performance found in synthetic motor oils.

The Importance of Changing Oil

Motor oil provides lubrication to the many moving parts of an engine, which helps to avoid damage and keep your engine running smoothly.

Each time your engine runs, by-products from combustion are collected in your engine oil. If contaminants build up beyond the capacity of the oil, they accumulate and create deposits, sludge and wear in the engine. The by-products can result in problems such as milky engine oil and metal shavings in the oil.

If the oil is not changed regularly, these contaminants can have a negative impact on your vehicle’s overall performance and efficiency. In addition to changing your oil when recommended, it’s important to keep up with regular vehicle maintenance and use a quality motor oil, such as one from Pennzoil.

So how often should you change your oil? Typically, it’s best to change your vehicle’s oil every 3,000 to 5,000 miles or your manufacturer’s recommendation. However, this is all dependent on factors such as your vehicle’s age, driving conditions and the type of oil you use.

Fortunately, many modern-day cars have engine oil indicators and will provide you with a warning signal on your dashboard when your oil is low or when to change the oil. Many dealerships or service centers will also put a sticker on your window with the date you will need your next oil change.

When in doubt, consult an automotive technician or your vehicle’s manual for recommendations. It’s always better to be on the safe side!

What Happens When Your Car Runs Out of Oil?

If your engine runs out of oil, parts will start to grind together since they don’t have lubrication, and the engine will seize up and eventually stall. This causes damage that is extremely difficult, if not impossible, to reverse. This is why it’s so important to check your oil level regularly and change your oil often!

In addition to your vehicle’s check engine light on your dashboard (if it has one), there are a few other signs to look out for that can indicate it’s time for an oil change.

• Engine noise: When motor oil is doing its job, it will lubricate the parts in your engine and as a result, keep the engine quiet. However, if your oil level is low or has completely run out, you may start to hear knocking or rumbling sounds. If this occurs, take your car in for an oil change immediately.
• Smelling oil inside the car: Smelling oil inside your car is a sign that you may have an oil leak. If you ever smell exhaust fumes or gas, your vehicle may be overheating. In either case, you’ll want to take your car in for a maintenance check as soon as possible.
• Exhaust smoke: It’s normal for your car’s tailpipe to emit translucent vapor. But if you ever notice that this turns to smoke, you may have an oil leak or faulty engine parts.
• High mileage: As stated previously, most vehicles require an oil change every 3,000 to 5,000 miles, or roughly every three to six months. If you put a lot of miles on your car one month, you may want to take your car in for an oil change a bit sooner to avoid any issues. This is especially the case if you have an older vehicle.
• Dark-colored oil: Clean oil is translucent with an amber hue. Over time, it will turn to a darker color due to collected contaminants and deposits. If you’re checking your oil and notice that it’s turning a dark color, this is a key sign it may be time for an oil change.

Learn More About Car Oil

To learn even more about motor oil, check out the following resources from Pennzoil, America’s most trusted motor oil and the first full synthetic motor oil made from natural gas:

• Pennzoil oil selector
• Pennzoil products
• How Pennzoil is made from natural gas
• Where to buy Pennzoil

As UTI’s official lubricants provider, Shell, Pennzoil and Rotella brands provide all lubricants to UTI’s Automotive and Diesel programs.¹ Shell also provides “life happens” fuel/Visa cards for students and more than $50,000 in annual scholarships!¹⁰ To learn more about how leading brands like Shell collaborate with UTI, check out our Aftermarket Relationships page.