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The difference in fuel types explained
Updated 10 Oct 2019
E10, 91, 95, 98 and even E85 – there are so many options out there when it comes to fuel.
So how do you know which one is right for you and your vehicle? Most petrol vehicles will happily run on any of these fuels, except E85 (more on that later), but which fuel should you run in your car to ensure you get the best fuel economy?
The different numbers associated with fuel are known as the ‘Research Octane Number’ or RON. Without going into an explanation that requires a scientific degree to understand, the RON rating of a fuel determines how much compression (heat) the fuel can handle before it pre-ignites in the engine.
Pre-ignition is less efficient and so increases fuel consumption and can also cause damage inside the engine.
If you’ve noticed a metallic pinging noise from your engine while you’re driving, this is most likely the fuel inside your engine pre-igniting.
In the old days, lead was used as an additive in fuel to help prevent pre-ignition, but was found to be detrimental to the environment and has been phased out completely.
If you purchased your vehicle new, you would have noticed the sticker on the windscreen claiming the average fuel consumption per 100km, and you may have struggled to prove that claim.
What you may not have known however, is that figure is based off using 95 RON premium fuel. The reason for this is that many European vehicles require 95 RON or higher fuel – as that is considered their regular unleaded.
Some performance vehicles require the use of 98 RON fuel. This fuel can be safely used in any modern petrol vehicle designed to run on 91 RON – it may even increase your fuel economy, which will negate the extra cost at the bowser.
Make sure you fill your vehicle with a fuel that’s RON number is equal or higher than what the manufacturer requires
. This is printed in the owner’s manual and many vehicles will also have a label on the inside of the fuel door.
So, what about Ethanol? Over the last 10 years, many manufacturers have upgraded their vehicles to be able to run on a blend of petrol and ethanol to combat the reliance on fossil fuels.
The most common Ethanol fuel is E10, which is a blend of 90% petrol and 10% ethanol. The other ethanol option is E85, which, as the name suggests, is a blend of up to 85% ethanol and 15% premium unleaded with a RON rating of 105.
Ethanol-based fuels are usually cheaper than the straight petrol counterparts, but ethanol holds less energy – so your vehicle will use more of it. Most E10 blends have a RON rating of 94, just under the premium RON rating of 95.
Unlike petrol, using ethanol in a vehicle that is not compatible will cause major damage to the fuel system and possibly the engine. This is especially the case with E85, as there are only a few vehicles designed to be able to run on this fuel.
Holden’s Series II Commodore and a handful of SAAB and Chrysler models are able to be run on E85. If you are not sure, it is best to check in your owner’s handbook or with your vehicle manufacturer. E85 has been the fuel used by the V8 Supercars series since 2009.
E85 compatible vehicles can also run on regular fuel and E10, or a mix of all three.
The Queensland Government have released a website https://e10ok.initiatives.qld.gov.au/ to check and see if your vehicle is capable of running on E10 – most vehicles built after the year 2000 are able to run on this fuel. The type of fuel best for your vehicle will depend on many factors and it is best to check in your owner’s manual to find which fuel is recommended.
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Finding a passion for cars from a young age, Joel carried out work experience as a mechanic whilst at school before starting an apprenticeship after finishing year 12.
After almost 10 years on the tools and in customer service, he moved into the IT realm as a Data Analyst and In-House mechanic at AutoGuru.