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Regular vs Premium Unleaded: Which is the Best for your Car?

Posted by AJ on

“Premium fuel” is supposedly better for our cars, yeah?

But what does “better” even mean?

Will our car suddenly become faster? Will we be able to drive a greater range on a single tank? Do engines explode if you use 95 instead of 98 octane? And are we taking our cars on a bender by using ethanol?

Think about it - there’s a lot we don’t know about the types of fuels available.

So, to help? We at Poncho Insurance are going to share with you what makes premium premium, and debunk all the other myths in between.

Uh… hang on, I’m new to this. So, there’s actually a difference between petrol and diesel?


But without getting too much into the chemistry, the only difference is that diesel molecules have about twice as much carbon. Translation: it burns in a different way to petrol.

Petrol is incredibly volatile, making it explode-happy; diesel’s actually quite hard to burn.

To combat this, petrol engines use a spark to ignite the fuel, whereas diesel engines use compression.

There are a lot more differences, but you only need to know one thing. Don’t put diesel in a petrol car, and vice versa. Otherwise there’ll be more explosions than a B-grade action movie

So how is regular unleaded different to ethanol fuel?

Good question. The biggest difference? How they’re made.

Petrol is made by cooking crude oil. The oil refinery process gets you all sorts of goodies, including petrol, diesel, kerosene, even the gas you use in the barbecue.

Ahem: please do NOT use this as a sign to cook with petrol.

Ethanol on the other hand? Made from natural waste, normally by fermenting old sugar cane crops, corn crops, beetroot crops, and other sugary scraps.

Despite their very different journeys to your car, they actually burn quite similarly. That means that some (mostly modern) engines are more than happy to receive fuel containing ethanol.

Before you chuck any old fuel in your car though, always read the instructions inside your fuel filler cap, or in your car’s instruction manual. Preparing engines to work with ethanol has only been a recent trend in the car industry, so a lot of old cars will look as drunk as a skunk if you try using ethanol.

Cool, that all makes sense. So, how is unleaded different to premium unleaded?

Those numbers at the servo (91, 95, 98, etc) all have a purpose - they’re known as the fuel’s ‘octane rating’.

An octane rating simply shows a fuel’s likelihood of burning too early. At high revs and large throttle openings, that can cause some serious damage to your car.

So, some cars don’t need a lot of protection against this, due to their design. They can probably accept any fuel - regardless of octane rating.

Some cars might be a bit more sensitive, and are at higher risk of damage taking low-octane fuels. They’ll probably ask you for premium, or above.

That’s the key difference between premium and regular - how much risk they pose to your car. But there are still a million myths around premium fuels we still need to answer:

A higher octane rating has more energy, and more power

That’s a big ole bunch of “nope” to that myth. Despite the octane rating, every fuel has roughly the same amount of energy stored within.

You must use the octane rating designated to your car

There’s a bit of truth to this one. If your car can only handle 95 or above, they mean it. But going above the recommended level is never a bad thing. Going below can be.

Buying premium is smarter, because the fuel savings pay for themselves

This myth is plausible, but unlikely. You’re likely to get a tiny improvement in either performance or fuel economy, depending on whether you put pedal to the metal, or cruise control to… cruise.

But say regular fuel costs $1.40/L, and premium is $1.55/L. You need to be driving around 10% further on each tank of premium, or getting places around 10% faster than you would otherwise on regular unleaded.

And it’s pretty unlikely you’ll ever see savings that extreme. So if your car is happy with a lower octane, don’t feel bad about buying the cheapie.

Use the extra money on a slushie.

Thanks, I learnt heaps! How can I learn more about driving and insurance myths?

Poncho’s got your back!

Check out the rest of the Poncho blog for more tips on driving, insurance, fuel, and everything in between.

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