What Happens if You Use the Wrong Engine Oil?

Tim Miller, 2 years ago

5 min read

  • Car ownership
  • Maintenance
  • Engine
Pouring engine oil

Guest contributor, Tim Miller, explains why it's important to use the right engine oil for your car.

Do you know what can happen if a person receives the wrong blood type transfusion? Your guess is as good as mine; it could be fatal. Similarly, motor oil is considered the lifeblood of the engine, and using the wrong type can have equally catastrophic consequences.

There is no substitute for the role of engine oil, which is why in this advice guide we will explain what happens when you use the wrong type of oil and how to go about fixing it.


What is engine oil?

What happens if you use the wrong engine oil?

How to fix it


What is engine oil?

Engine oil, also known as motor oil or engine lubricant, is a viscous liquid distilled from crude oil that is used to lubricate engine parts. It has two primary ingredients: base oil and additives. Engines have many moving parts that can rub against one another, causing friction. The engine oil performs many functions in letting an engine and its internal components work properly.

Topping up a car's engine oil

However, its primary function is to lubricate the moving parts of an engine. Other important functions include coating and protecting moving parts, cooling, sealing and reducing friction.

What happens if you use the wrong engine oil?


Although the brand of engine oil you use is essential, it isn't as crucial as the viscosity grade. Engine oils come in various grades (5W-30, 15W-40, 10W-30, etc.), each designed for a specific type of engine.

While some viscosities are appropriate for cold climates, others are better suited for warmer temperatures. The right engine oil allows your car to last as long as possible. The engine gets the best protection and performance when you use the recommended oil, whether conventional, synthetic or a different viscosity.

That's why it's always best to follow the manufacturer's specifications when it comes to topping up your oil as bad things always happen when these specifications are ignored or overlooked. Oil leaks, overheating, reduced fuel economy, and a damaged engine are all reasons why you should follow the recommendations in your owner's manual. More specifics about these symptoms are provided below.

Oil leaks

The use of wrong engine oil can cause oil leaks since various synthetic engine oils will have different flow features; you may notice a leak under your car or where it's parked. High mileage or older cars from the 1960s and 1970s use thicker oil to help seal and protect the engine. On the other hand, modern vehicles are designed to use thinner oil.

A puddle of dark brown engine oil that has leaked from a car.

Using synthetic oil instead of conventional oil in an older or higher mileage vehicle can cause gaskets and seals to leak. If it's too thin, it will not provide the adequate lubrication and protection needed. Oil leaks are a complete mess, and you would need to address them immediately.

Engine overheating

Overheating can happen if you don't use the recommended oil for your engine. An engine oil's job isn't just to lubricate the engine's various parts; it also absorbs some of the heat produced by the engine, making sure that none of the parts overheat.

Using a thicker oil against the manufacturer's recommendation can result in less flow and the oil's inability to balance temperature. For the wrong application, the greater the oil thickness, the greater the resistance and heat generated.

This guide covers all the reasons why your car might overheat.

Reduced fuel economy

If you notice a drop in fuel economy after an oil change, it could be due to the wrong oil. Using an engine oil with a higher viscosity (an overly thick oil) than what is recommended can reduce a car's fuel efficiency.

A highly viscous oil will need more energy to pump, resulting in increased fuel consumption. To overcome the high resistance on moving parts, your engine will need to burn more fuel. Changing to a moderately thinner oil should result in improvement in fuel efficiency. Make sure to use the appropriate weight and type for your vehicle.

Find out how to get the best fuel efficiency from your car.

Damaged engine

The wrong engine oil can cause engine damage because it does not properly lubricate its components. This will lead to metal-on-metal contact since the moving parts are not being lubricated. Friction quickly follows, causing engine parts to wear. It also has the potential to damage your engine's bearings, cylinder surface, oil pump, pistons, and other components. As a result this will certainly cause the engine to fail at some point, thereby shortening the engine's life.

How to fix it

Mechanic changing oil engine

If you notice any of the above symptoms, you should have your vehicle inspected at your local garage and the oil changed to prevent further damage.

WhoCanFixMyCar can help you solve the problem. We'll assist you in finding reliable car repairs that won't cost the earth, so you can get your car back in working order in no time.

Did you know that you could save an average of £34 by booking your next oil change through WhoCanFixMyCar?


Finally, you should only select the oil viscosity that is strongly advised for your engine and driving conditions. To find out which oil your car needs, click here.

The wrong engine oil can decrease your vehicle's performance and cause engine damage. The cost of purchasing the recommended oil is far less than rebuilding an engine. Always consult your owner's manual to find the right engine oil for your vehicle.

You can also use WhoCanFixMyCar to compare the prices, reviews, and locations of the best garages in your area with just a few clicks, allowing you to save more and stress less.

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