Back to Latest News
What Petrol Should I Use?
When you pull up to the bowser at your local fuel station, you’ll see a variety of pumps with different labels. You probably know which fuel is meant to go in your car, but have you ever wondered what the differences are and what happens if you use the wrong fuel?
With decades of experience in the mechanical industry, the team at Donnellans are able to help you out with all of your fuel related questions.
If you have a diesel vehicle, keep an eye out for our upcoming article about different ways to charge electric vehicles and another about the different grades of diesel fuel available in Australia (spoiler alert: at the time of writing, there’s only one grade of diesel in Australia).
Petrol is made from petroleum, itself a refined product made from crude oil, which is pulled from the ground by tapping into massive underground reservoirs all over the world.
All petrol designed for use in Australia is unleaded, since added tetraethyllead was phased out in 2002 due to health concerns regarding lead in exhaust emissions. Lead was originally added as a cleaning agent and lubricating additive which helped avoid engine inlet and exhaust valves being damaged over time. Lead also helped with avoiding knocking or pre-detonation.
Leaded fuel is still widely used in aviation, so if you live near a light airport, you’re probably still being exposed to trace amounts of lead through your environment.
What Do the Numbers on Fuel Pumps Mean?
Let’s begin with what the numbers mean. Frequently you will see pumps marked with 91, 95 or 98. This is the Research Octane Number of the fuel, or RON for short.
Higher RON numbers mean that the fuel is more resistant to pre-detonation, or ‘knocking’. Many modern engines can detect knock and change timing or fuel delivery to avoid engine damage.
Standard Unleaded Petrol (91)
Standard petrol across the country is 91 RON. It can be found at just about every fuel station you drive to, many older cars run just fine on plain 91, while some modern vehicles can operate on 91 at reduced performance levels.
Curiously in Australia, 91 fuel has a lot looser regulations when it comes to particular chemicals, including sulphur, which can damage sensitive emissions control components on more modern vehicles, this is why 95 is the minimum recommended fuel for many cars.
Many European countries no longer sell 91 RON fuel, as it’s too crude to meet many emissions standards.
Running 91 in a vehicle that is meant to be used with higher grades of fuel may result in knocking, or pre-detonation. Over time, this can cause severe engine damage
Premium Unleaded Petrol (95)
Bowsers with ‘95’ on them stock Premium Unleaded Petrol. This fuel is essentially the same as 91, but undergoes more stages of filtering and refinement.
Premium fuel is a cleaner burning and results in more efficient economy figures for vehicles modern enough to take advantage of the extra anti-knock capabilities.
Unlike 91 fuel, 95 has much more tightly regulated sulphur content levels, which means they’re suitable for modern vehicles with petrol particulate filters (PPFs).
The higher RON figure means this fuel is suitable for many European and Japanese vehicles that specify 95 as the minimum recommended fuel grade due to being fitted with turbochargers or higher compression motors.
Premium fuel typically costs 10-15 cents per litre more than standard 91. This cost comes from the extra processing and refinement.
Ultra Premium Unleaded Petrol (98)
Premium 98-octane fuel is the highest quality unleaded fuel commonly available in Australia, compared to 91 and 95, it has undergone even more refinement and filtering to provide more efficient engine operation, greater knock resistance, less pollution, as well as higher engine power and performance.
Typically vehicles that state they require a minimum of 98-grade fuel are very high performance models that feature turbochargers, superchargers or high-revving motors with ultra high compression. Using 98 in these vehicles unlocks peak performance
Vehicles that specify lower grades of petrol can often run just fine on 98 but may not have the ability to take full advantage of the extra knock resistance offered by 98 fuel so you’re just wasting money putting this fuel in a lower grade vehicle.
Ultra Premium tends to cost around 10 cents per litre more than 95.
E10 Fuel
E10 fuel is unleaded petrol spiked with 10% ethanol. Roughly equivalent to 94 RON ULP, it’s the first widely accepted step towards moving away from fossil fuels by creating alcohol from grain.
We’re not able to take a deep dive into how much land is required for ethanol production but while it’s not a silver bullet for climate change, ethanol production helps support the local sugarcane and corn industries, which is great.
Ethanol is slightly less energy dense than petrol, that means that per tank of E10, there is less energy than a tank of petrol, therefore you’ll use fractionally more per km.
Ethanol based fuels are slightly corrosive, so unless your vehicle has been certified safe for E10 fuel or has had the fuel system upgraded to modern standards, stick to regular ULP
E85 Fuel
If you were paying attention, you can probably guess that E85 is a blend of 85% Ethanol and 15% premium unleaded petrol. Comparing this fuel to the RON ratings we previously discussed, E85 is roughly equivalent to 107 grade petrol.
In Australia, this fuel is most well known as the official race fuel of the Supercars series. Frequently referred to as ‘Flex Fuel’, this fuel is a favourite amongst ultra high performance and modified vehicles.
E85 fuel is great for performance vehicles for two reasons: firstly, the superior knock resistance means you can tune your engine for far greater power levels while still having a safe and reliable tune, and ethanol fuels have a cooling characteristic that helps keep internal engine temperatures under control.
Sounds great, but don’t expect your fuel economy figures to go up with ethanol based fuels, as the fuel is less energy-dense, you’ll be burning a lot more of it. With some people seeing a reduction in range by up to 40%.
Does It Matter Which Fuel You Use?
There’s a quick and easy answer to this question. Yes.
Generally you can put a higher grade fuel in your vehicle without worry, but it’s highly recommended not to run a spec fuel that’s lower than what your manufacturer has stated.
While many modern vehicles will adapt to a lower rated fuel at the cost of performance and economy, you risk pre-detonation and potential engine damage over time by using the wrong fuel.
In many cases, running a higher grade fuel that what your vehicle was designed to use won’t net you any benefits unless your vehicle is modified or re-tuned to take advantage of the higher grade fuel.
You can find your manufacturer's recommended fuel grade in your owner's manual, or by contacting Donnellans, we can let you know all sorts of information regarding your vehicle.
