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What's the difference between a conventional and synthetic oil change?

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Updated 31 Oct 2019

Jason Unrau

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Unless you drive an electric car, oil changes are part of the monotony of car ownership.

Once or twice per year minimum, you’ll have to pay for that liquid gold to be drained from your engine and disposed of, just to have it filled with more engine oil.

But when you have the choice between a conventional and synthetic oil change, what’s the difference?

Is there actually a benefit to using synthetic oil in your engine?

The Chemistry Behind Conventional and Synthetic Oils

Conventional and synthetic engine oils both start in the same place: in the ground.

Crude oil is refined to create the base for both fluids, but they go down different paths from there.

After the refinement process, detergents, dispersants, anti-wear agents, friction modifiers, anti-oxidants, and rust inhibitors are blended into the base to make conventional oil.

Every manufacturer has their own ‘special recipe’ to achieve the quality they want.

Synthetic engine oil goes through a different process.

It’s refined much further than conventional oil so the molecules are more uniform in shape and size, as well as to remove even more impurities.

Think of it as the difference between rocks and marbles.

From there, synthetic oil receives a blend of additives also, albeit usually of a higher quality.

You Mean It Isn’t Just Oil?

It’s true, both conventional oil and synthetic motor oil contain additives not derived from oil.

These particles serve specific purposes such as preventing corrosion inside the engine, coating components better, degrading at a higher temperature, and even further reducing friction between moving parts.

Synthetic engine oil does a better job of protecting your engine due to its stringent manufacturing process.

Is Synthetic Oil Better for Your Engine?

If synthetic oil is that much better than conventional, you’d expect that it would be used for every car, wouldn’t you?

Here’s the thing: for most cars and their usage, synthetic oil is overkill.

When it’s serviced regularly, conventional oil does a good job protecting your engine.

Some cars, however, require synthetic engine oil, no questions asked.

High-performance or high-displacement engines need the added protection that synthetic fluids provide.

Older engines benefit from reduced friction.

And one growing vehicle segment – turbocharged engines – require synthetic oil to adequately lubricate the turbo.

How It Affects Your Oil Change

If you use synthetic oil, you might be tempted to extend your service interval between oil changes.

That’s not a good idea.

While it might offer better protection, it doesn’t mean you can delay maintenance – especially if your engine demands synthetic oil.

Stick to your manufacturer’s recommended oil change interval!

Some manufacturers also make oil filters specifically for synthetic oil.

Improved filtration removes more contaminants and impurities, keeping the oil cleaner for longer.

It’s a good idea to use a filter designed for synthetic oil, but it’s not mandatory.

You can be sure that the high-quality mechanics on AutoGuru will only use the appropriate oils and filters for your car.

If you’re in need of a service, you can a local mechanic online within minutes, it’s easy!

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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.