Fuel for thought

With so many fuel options available, which one is right for your car?

Filling up at a petrol station is becoming increasingly complicated with different varieties and brands of fuel available. We asked RACQ’s Specialist Motoring Advisor Bruce McLeish to help decipher the main causes of pain at the pump.

What is octane?

An octane rating is a measure of a fuel's ability to resist a phenomenon known as ‘knocking’. The higher the Research Octane Number (RON), the more compression a fuel can withstand and the less likely it is to ‘knock’ or burn too early inside your engine.

If fuel burns too early a driver may hear pinging or knocking noises coming from their engine. Knocking can cause serious damage so take your car to your mechanic if you hear unusual noises coming from your engine.

What’s the difference between 91, 95 and 98 petrol?

These numbers represent the octane rating (RON) of the fuel.

Australia’s current standard fuel is 91 RON and most cars sold since 1986 were built to use it effectively. 

Ninety-five and 98 have a higher RON and are considered premium fuels.

You can find your engine’s octane requirement in your vehicle’s handbook.

Why do some cars need premium petrol?

The engines in cars that require premium fuel have a higher compression ratio than cars designed to run on 91 RON. These engines are often more powerful and fuel-efficient.

If your car’s handbook says it requires premium fuel, you’ll need to use 95 or 98. Some cars may specify 98 only so it’s important to check that you’re using the right fuel for your vehicle.

Using a lower octane fuel than specified, such as 91 in an engine designed for 95 or 98, can damage your engine.

Can I use a higher-octane fuel than recommended?

Yes, but using a higher-octane number fuel than required will not necessarily produce noticeable benefits. You may have better fuel economy with a higher-octane fuel but the higher cost of 95 or 98 will likely cancel out any benefits. 

What’s E10 and can I use it in my car?

E10 fuel is a blend of up to 10% ethanol and 90% unleaded petrol.

Ethanol is an alcohol made from vegetable matter such as sugarcane and corn so it’s a renewable local resource that produces less greenhouse gasses than petrol.

E10 is usually cheaper than the standard 91 unleaded but it has less fuel economy so you may find yourself filling up more often. To offset the increased consumption, you should look for E10 that is at least 3% cheaper than 91.

Most petrol vehicles sold in Australia after 1986 can use E10 but it’s not recommended for cars sold prior to 1986 or those fitted with a carburettor. Visit E10 OK? to find out if E10 is suitable for your vehicle.

What can I do to save fuel?

There are a few things you can do as a driver to improve your fuel economy such as driving as smoothly as possible and avoiding accelerating harder than necessary.

It’s also important to have your car properly serviced regularly to ensure it’s running smoothly.

You should also think about fuel efficiency when choosing your next car. A car that’s bigger and more powerful than you need will end up costing more in fuel and operating costs.

Should my next car be petrol or diesel?

Whether you choose a petrol or diesel car depends on your individual circumstances.

Diesel cars are usually more expensive than petrol cars but they are more fuel efficient. 

If you do a lot of long-distance driving the fuel savings can add up making the diesel car cheaper overall. 

Petrol cars are better suited to short distances and city driving.

Do you have a curly car question? We can help with advice relating to the use and ownership of a motor vehicle in Queensland. Call our Motoring Advice team on 3666 9148.