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Engine Oil 101: Everything You Need to Know

September 24, 2020

Taking care of your car engine is a must and perhaps the easiest way to do so is by getting a regular oil change. Engine oil is the lifeblood of your car – without it, the engine would seize up. Neglect regular oil changes and you are asking for catastrophic engine failure. The good news is that getting a regular oil change is cheap, quick, and you can even do it yourself. We’ve unpacked everything you need to know about engine oil and whether you’re throwing money by changing your oil too frequently.


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What is Engine Oil Used For?

The primary role of engine oil is to lubricate moving parts in an engine. Oil keeps the parts running smoothly while minimizing friction and engine component wear. It also draws heat away from lubricated engine components before the oil is cooled via air in the sump before being recirculated through the engine.

It does this via your vehicle’s oil system which is made up of the following parts:

Additionally, motor oil also has several chemical compounds that improve its performance and help keep your engine clean by removing impurities.

Common additives found in motor oil include:

Five Functions of Engine Oil

How Does an Oil Change Help My Car?

Regularly scheduled oil changes are necessary for good engine health, but have you ever wondered why changing your oil is so important?

Modern oil is much more advanced than it used to be, which means we no longer have to change the oil every 3,000 miles. The role of oil however hasn’t changed much and it performs the same functions with greater efficiency. If oil isn’t changed it eventually thickens and becomes tar-like as it breaks down and becomes what mechanics call engine sludge.

Engine sludge sticks to engine parts as it moves around the engine and diminishes the oil’s ability to lubricate and clean. It causes blockages in the engine’s oil passages which can result in oil starvation. Heat from the engine causes engine sludge to harden which can cause major problems for fuel injectors, pistons, and valves. It can also cause hard starting, overheating, and power loss.

Ignoring engine sludge can expose your vehicle to extensive engine damage and removing it requires the oil to be drained and the engine to be flushed. If sludge is still present after an engine flush, it may need to be mechanically removed. The easiest way to prevent engine sludge and keep your engine running optimally is by having regular oil changes.

What Happens If I Don’t Get an Oil Change?

It might be tempting to skip an oil change if you’re hard-pressed for time or money. But not changing your engine oil is one of the worst things you can do for your car engine. It can also lead to some expensive consequences.

The first problem you will face is debris and contamination being deposited throughout your entire engine. Your oil keeps the engine clean by picking up dirt and anything else that shouldn’t be there filters it through an oil filter. When the oil filter becomes clogged with contaminants, the dirty oil is cycled back through the engine.

As contaminants build-up, the oil becomes abrasive, picking up more particles each time it cycles through the engine. Over time, contaminated oil wears down engine parts, and the engine has to work harder to keep the sludgy mess that was once your oil moving around.     

Can a Car Run Without Engine Oil?

Engines are designed to consume oil. As a car ages, oil consumption becomes more of an issue. If your oil is too low, your vehicle may be at risk of overheating since part of the oil’s role is to help remove heat from moving parts. This could lead to a blown head gasket or warped engine internals – both serious and expensive problems to repair.

How Often Should Engine Oil Be Changed?

Ask three people how often you should change your engine oil and you will very get three different answers. As oil and automotive manufacturers implement the latest research and technology, the old rule of changing oil every 3,000 miles no longer applies.

This is the recommended oil change interval for some of America’s best-selling vehicles:

As you can see, there is a huge difference between recommended oil change schedules between manufacturers and types of car. There are a few reasons for this disparity based on the type of oil recommended by your vehicle manufacturer, the type of engine in your vehicle, and the conditions that you will likely be operating your vehicle in.

When in doubt, it’s better to get your oil changed more frequently than not as motor oil degrades over time. The longer you leave old oil in your engine, the more it will break down. Additionally, its lubricating and cooling properties will greatly diminish. But keep in mind, the manufacturer knows your car best, so by sticking to their recommended oil change schedule, you will ward off most mechanical problems over the lifetime of your vehicle.

Can I Simply Add Oil Instead of an Oil Change?

Why replace engine oil instead of just adding to it? It’s a pretty good question and not as straightforward as you might think. While it’s possible to add new oil to old oil, this should only ever be done in case of an emergency, for example, if your car has very low oil and you need to drive straight home (and then following up with an oil change).

When you combine dirty and fresh engine oil the old oil doesn’t just disappear. Instead, you’re watering down the new oil and decreasing its ability to perform. The oil will be thick instead of honey-colored and have a gritty texture to it – definitely not what you want circulating inside your engine.

And if you haven’t replaced the engine oil the oil filter wouldn’t have been replaced either, meaning all that dirt and debris isn’t being removed by the engine oil just keeps getting transported around the engine and coming into contact with moving parts. Instead of lubricating the engine components, the debris and contaminants will create additional friction and cause damage to engine internals.

 If you’re finding that your oil level is lower than it should be when your car is due for an oil change, it’s an indication that your vehicle is burning oil and your mechanic will need to investigate what’s causing it.

Different Types Of Engine Oils Explained

Fully Synthetic Oil

Fully synthetic motor oil has been completely chemically engineered to make the molecules uniform. Therefore, it performs more consistently with fewer impurities than conventional oil molecules. Fully synthetic oil has higher viscosity levels, better resistance to corrosion, and oxidation. It is typically the most expensive type of oil available and is recommended for high-performance engines or vehicles that are used for towing.

Semi-Synthetic/Synthetic Blend Oil

Semi-synthetic motor oil is a hybrid that combines synthetic and conventional base oils for improved resistance to oxidation with exceptional low-temperature properties. It is a good option for those who want extra performance from conventional oil without the high price tag of fully synthetic oil.

High Mileage Oil

If you drive a car that has traveled more than 75,000 miles you may need to switch to ‘high mileage oil’. This type of oil contains unique additives to protect seals, prevent oil leaks, and reduce oil burn-off, engine smoke, and engine emissions.

Conventional Oil

Conventional motor oil is considered the industry standard. It is manufactured from crude oil that has been refined and is available in a wide range of viscosity grades. It is mostly used in late-model cars that are driven daily and don’t require special protection.

What Do The Numbers On The Bottle Mean? Motor Oil Grades Explained

Arguably, the most important property of oil is its viscosity rating. Look at the label of any bottle of oil, and you will find a series of numbers and letters, for instance, 10W-40. This is the ‘grade’, which indicates that particular engine oils viscosity.

Viscosity is a universal measurement of the movement of a fluid. It refers specifically to the oil’s resistance to flow at a certain temperature. This can be broken down into two key characteristics: kinematic and dynamic viscosity. Understanding these will help you choose the best oil for your vehicle.

Kinematic viscosity measures the oil’s internal resistance to flow and shear under gravitational forces. The lower an oil’s viscosity is, the faster it will flow. Kinematic viscosity also determines the high-temperature grade of oil. On an oil graded 10W-40, Kinematic viscosity refers to the ‘40’.

The other measure of viscosity is dynamic viscosity. Dynamic viscosity is a measurement of the amount of energy needed to move an object through the oil. Dynamic viscosity also determines the low-temperature grade of oil. On an oil graded 10W-40, dynamic viscosity refers to the ‘10W’. The ‘W’ literally stands for ‘winter’ – an indication of the oil’s resistance to cold at engine startup.

What it all comes down to is that the lower the first number is, the less resistance to flow the oil has when you cold start your engine. And the lower the second number is, the less resistance to flow the oil has at normal operating temperature. Motor oils get thicker as the temperature cools and thinner when heated. Therefore, thinner oils with low viscosity provide more protection at colder temperatures. Thicker oils with high viscosity provide more protection at hotter temperatures.

How To Pick The Right Motor Oil For Your Vehicle

Now you know the difference in engine oils, you might be considering if it’s worth changing to a higher-performing oil. Before you change oil types, you should always consult your vehicle owner’s manual as using the wrong motor oil can cause engine problems.

Using an oil that is lighter than necessary can cause excessive engine wear as the oil is too thin to form a protective film between the parts. Using a heavier oil than necessary will decrease fuel economy, increase engine load, and slow the rate of oil flow. Both instances will lead to shorter engine life. Your mechanic will know if you are using the correct oil for your vehicle, and when it’s time to switch to a heavier or lighter grade.

Benefits of Using Synthetic Oil

Synthetic oil is more expensive than conventional oil but also offers some very unique benefits to make it worth the extra cost in certain situations. For those that live in the city and only drive a short distance every day to work and then home again, conventional engine oil likely won’t get up to operating temperature, never burning off excess moisture. This causes it to break down at a much faster rate. Synthetic oil flows must easier in extreme temperatures and have greater lubricating properties than conventional engine oil, even on short trips.

For a car engine using conventional or mineral oil, it’s recommended to have the oil changed every 3,000 – 5,000 miles. Running synthetic oil means it isn’t required to be changed as often as it is more resistant to breaking down, so it maintains its properties for longer. Synthetic oil still needs to be changed according to the manufacturer’s recommendation, but engines designed to use synthetic oil have longer intervals between oil changes such as 10,000 – 15,000 miles.

Synthetic oil typically contains high-performing additives in the form of dispersants and detergents to enhance its ability to remove contaminants and keep an engine clean, reducing engine wear and potential damage. 

Is Synthetic Oil Made From Natural Gas Better?

Synthetic oil is made in a laboratory and used to be extracted from crude oil or one of its byproducts. Around the 1970s, oil manufacturers such as Shell started to look at cleaner sources and ways to make synthetic oil. Synthetic oil made from natural gas is free of the impurities found in crude oil, with the result being a cleaner and more pure product.

Molecules in synthetic oil made from natural gas are easier to separate and make uniform, giving it lower volatility (how readily it vaporizes at high temperatures) leading to better performance in extreme temperatures. And although the process of turning gas into liquid is extremely complex, using a resource that is a greenhouse gas, cheaper than crude oil, and an abundant supply offers several environmental and cost benefits compared to conventional oil.

Synthetic oil made from natural gas is ideal for high-performance or turbocharged engines, and those operating in harsh conditions or extreme temperatures. 

What Is The Best Engine Oil For Diesel Engines?

So far we have only discussed oil for petrol-powered engines. When it comes to the best oil for a diesel-powered vehicle, things get a little more complicated. Although, at the surface level, both gas and diesel motor oils appear to have similar makeups.

The difference exists primarily due to the different exhaust and emissions systems in diesel-powered vehicles. Oils suitable for diesel motors have zinc dialkyldithiophosphate added to it which reduces engine wear and prevents corrosion. Emission systems in diesel engines are designed to be able to deal with this additive, but putting this oil in a gas-powered vehicle would cripple the catalytic converter, making the car run poorly.

Diesel oils also have more additives than oils suitable for gasoline engines. Diesel motors produce more waste products like soot which end up in the crankcase. The additional detergent additives in diesel engine oil remove these effectively. In a gasoline engine, the higher number of additives would cause damage to pistons and seals, resulting in lost engine compression.

Finally, diesel engine oil usually has a higher viscosity. A gasoline engine would struggle to move this oil around sufficiently, and the oil pump in a gas-powered car would struggle to deliver it where the motor oil is needed most at start-up.

As we recommended for owners of petrol-powered vehicles, the best way to choose the right motor oil for your diesel is to consult your owner’s manual and get a recommendation from your mechanic. They will have a pretty good picture of your vehicle’s health and know when a different grade oil is required.

What is an Oil Pressure Sensor?

Your engine’s oil pressure sensor has a very important job of recording and constantly monitoring internal oil pressure. When a change in oil pressure is detected, a thin membrane on the sensor deforms, alerting the ECU (engine control unit) that there is a problem with oil pressure, triggering a warning light on the dashboard that alerts the driver. For your car to regulate oil flow and oil temperature, the oil pressure sensor must be working.

The sensor itself can be found bolted into the engine block, sometimes between the oil pan and oil filter, and sometimes it can be found behind the intake manifold. It’s connected by an electrical chip to the ECU so care needs to be taken when replacing it.

If an oil pressure sensor malfunctions, it will trigger an oil pressure warning light and this problem can be easily resolved by replacing the oil pressure sensor. Identifying and testing a faulty oil pressure sensor is a simple job for a mechanic and they will test it before replacing it as several conditions can trigger a low oil pressure warning such as a leak in the oil line or corroded wiring around the electrical plug that holds the oil pressure sensor in place. 

Can You Drive with a Bad Oil Pressure Sensor?

We know how important having good oil pressure is for an engine and how quickly oil starvation can completely destroy it. We know that when your oil pressure sensor detects a problem with oil pressure it will trigger a warning. What we don’t know is exactly what has triggered the oil pressure sensor in the first place.

In fact, any of these symptoms will trigger an oil pressure warning light:

Without performing further tests to identify the problem, it’s impossible to know if a car showing signs of low oil pressure is safe to drive. At the very least you might not destroy your engine. At the worst, you could overheat the car, blow a head gasket or seize the engine entirely.

When a car shows signs of low oil pressure it should be taken seriously. Pull over as soon as possible and shut off the engine to avoid further damage. The problem should be diagnosed and repaired by a qualified mechanic as soon as possible.

Can I Change My Own Engine Oil?

A DIY oil change is one of the easiest jobs you can do on your car. It requires few tools and minimal mechanical knowledge. It’s a job that is difficult to mess up, unless you use the wrong oil or forget to tighten your oil drain plug.

Changing your own oil as easy as buying the recommended amount of oil from an auto parts store, using the manufacturer’s recommended oil grade, buying the correct oil filter, and gathering the parts you need to perform an oil change.

There are thousands of excellent tutorial videos on YouTube that explain how to change your own oil. Where people tend to mess up is thinking that changing their engine oil and oil filter is all they need to do. When your mechanic performs an oil and filter change according to your manufacturer’s recommended service schedule, they will also have a long list of checks to perform on your vehicle’s cooling system, braking system, fuel system, transmission, and more.

Now you understand how engine oil keeps your car healthy, the most convenient way to get your car’s oil checked or changed is by scheduling an appointment with our mobile technicians at a time and place that suits you by calling (877) 907-6484 or booking an appointment online.