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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 Does Engine Oil Do

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:

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.     

It may not be noticeable depending on the age of your car, but 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.

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.

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.

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.