• engine

How does my choice of engine oil affect my car?

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Updated 11 Oct 2019

Jason Unrau

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You’re always looking for an edge.

Whether it’s better acceleration off the line in your Holden Commodore, better top-end speed from your BMW M Series, or a few extra clicks in range from your old Veedub diesel, you want to squeeze the best out of your engine.

Engine oil has long been touted as the solution for more power and better fuel efficiency, but is it true?

Engine Oil DOES Affect Performance

Wonder no longer.

The oil you choose for your car’s engine makes a difference in its economy and power production.

Engine oil viscosity is the main focus here, and it all boils down to the basic laws of physics.

The lower the engine oil viscosity, the better.

That’s why you see oil grades changing from the traditional 10W-30 to 5W-30 or 5W-20, and more recently, 0W-20.

At lower temperatures, engine oils with lower viscosity like a zero weight (that’s the 0W) are more fluid than higher weights.

That matters for one reason: resistance.

Your engine has to work harder to move internal parts with thicker oil in the crankcase, sapping energy before you ever have a chance to use it.

Imagine the difference between stirring a cup of molasses with a spoon opposed to a glass of water.

Not only is it impossible to match the stirring speed with molasses, but it takes more energy.

That’s how it works for moving parts in the engine crankcase.

Conventional Oil vs Synthetic Oil

By and large, the best oil viscosity is found in synthetic oils.

That’s only because it’s extremely difficult for oil manufacturers to obtain the same properties in conventional oil.

When you lower the friction and resistance inside the engine, like you do when you choose a low-viscosity synthetic oil, your engine doesn’t need to work as hard.

It can rev up faster and, potentially to a higher max RPM.

And because there’s less energy needed to do it, less fuel is required to obtain that power.

How Much Difference Is There?

It sounds great, doesn’t it? But how much gain is there?

With one high-performance car test with a leading synthetic oil, torque improved by less than 1 per cent and horsepower was up around 1.5 per cent.

Fuel efficiency gains were better – up nearly 1 mile per gallon.

Wait a sec… that’s not exactly gangbusters for gains!

While the truth is that you’ll squeeze more power and economy from your engine with a low-viscosity synthetic oil, you may not actually notice the difference.

Which Oil Should You Choose?

Don’t take the minimal gains as a detractor for synthetic oil, though.

It’s still the best choice for your engine, even if it’s not like a rocket booster strapped to the back bumper.

The best benefit of synthetic oil isn’t for more power or fuel efficiency, but that it reduces engine wear by up to 90 per cent.

Use your car manufacturer’s recommended grade of oil – just switch it up to synthetic to get the benefits.

A qualified mechanic on AutoGuru can recommend what oil to put in your car at your next service and it’s quick and easy to book in online, what are you waiting for?!

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Written By

Jason Unrau

Jason is a Canadian automotive content writer with a background in the auto service industry, but he’s been hooked on cars and mechanics since childhood.

One of his first cars was an ’80 Mazda RX-7 that’s sorely missed to this day. A ’68 Ford Torino GT, a ’66 Ford Country Squire Woodie station wagon, and a ’96 Suzuki GSX-R 750 have spent time in his fleet of cars, bikes, and trucks over the past two decades.

Jason’s pride and joy is under construction – a turbocharged ’88 Mazda RX-7 convertible. Also on his resume is CASCAR official certification.