Ethanol versus petrol FAQ

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Confused about ethanol-based fuels? This FAQ demystifies the world of ethanol-based fuels with information on performance, suitability and environmental benefits.

Ethanol is a renewable biofuel when derived from crops like corn and sugar cane.

How does the composition of ethanol-blended fuels differ from petrol?

Ethanol is produced by fermenting sugar, grain, yeastsi. It is a renewable resource unlike the fossil fuel-based petrol, which is non-renewable, being derived from oilii. Ethanol is currently sold blended with petrol, most commonly as E10 (containing 10% ethanol), however, recent developments of E85 (containing 85% ethanol) offer a more sustainable and renewable alternativeiii.

How much more environmentally friendly is ethanol than petrol?

On a simple litre-per-litre basis, ethanol produces 1.5kg of carbon dioxide (CO2) compared to 2.2kg produced by petrol. However, ethanol produces less energy than petrol so 1.4L of ethanol (which produces 2.15kg of CO2) contains the same amount of energy as 1L of petroliv. While this suggests the difference to the environment is small, the CO2 produced by ethanol-blended fuel use is countered somewhat by the CO2 consumed by the plants used to produce the ethanol, with estimates attributing a carbon dioxide saving of 70% once all production and distribution factors have been taken into v.

Do ethanol-blended fuels achieve the same level of fuel efficiency as petrol-based fuels?

As mentioned above, you need to burn 1.4L of ethanol to achieve the same amount of energy as burning 1L of pure petroliv. E85 blended fuel has about 33% less energy than petroliv. With ethanol-blended fuel the fuel efficiency is less and so fuel consumption increases to compensate for the decrease in energy outputvii.

Will my vehicle be able to function on ethanol-blended fuels?

BP guarantees any vehicle manufactured after 1986 designed to use regular ULP can use their E10i. However, some motor vehicles, particularly older models, are unable to operate with ethanol-blended fuel as their rubber seals and gaskets can be damagedvii. Consequently it is important to find out whether your vehicle can run on fuel containing ethanolviii.

Can ethanol-blended fuels be used in two-stroke engines?

Ethanol is generally not advisable to use in boat engines due to the risk of water contaminating the fuel. For use in other engines such as lawnmowers, leaf blowers and chainsaws, consult the manufacturer and ensure ethanol-blended fuel is not left in the fuel tank for more than a few weeksi.

Do ethanol-blended fuels or petrol-based fuels cost more?

E10 frequently costs less than regular unleaded petrolix. However, because consumption is higher with E10 than petrol, the overall running cost might not be lessx.

Do ethanol-blended fuels have a higher octane rating than petrol-based fuels?

An Octane rating measures a fuels anti-knock ability. A higher rating means the fuel can be run in higher compression engines, resulting in greater efficiency. Ethanol has a greater octane rating than petrol so it can be used in higher compression engines. However, the amount of compression provided by a car engine is usually already set for petrol. This means that using ethanol doesn't give greater power and efficiency since greater compression is not occurringiv. Holden's V8 supercars have been modified to handle higher octane ethanol fuels since the 2009 racing seasonxi.

Holden's Commodore range (VE Series II) are equipped with E85 (85% ethanol) capability (source: xii; image source: Holden).

Does the government put any restrictions on the amount of ethanol in fuel?

The Australian government's progressive roll-out of the Fuel Quality Standards Act 2000 is designed to ensure that consumers know exactly when they are putting ethanol in their carxii. This is crucial especially for owners of older cars as their engines may not necessarily be equipped to cope with ethanol-blended fuelsxiii. Up till 2012, the maximum amount of pure ethanol allowed in fuel was 10%; however, the Australian government now allows the sale of E85 fuelxiv.

i Office of Biofuels, New South Wales Government, 2013, Biofuels FAQ,

ii Manildra Group, 2008, Ethanol,

iii Office of Biofuels, New South Wales Government, 2013, Biofuels in New South Wales, and United, 2012, Ethanol 85,

iv Cadogan, J. 2010, Car Advice, 'Ethanol Versus Petrol: The Basics',

v Derry, N., Victorian Curriculum and Assessment Authority, 2007, What are Biofuels?,

vi U.S. Energy Information Administration, Department of Energy, 2013, How much ethanol is in gasoline and how does it affect fuel economy?,

vii Cars Guide, 2011, Can I run my car on E10 fuel?,

viii Federal Chamber of Automotive Industries, 2013, Environment & Fuels: Can my vehicle operate on Ethanol blend petrol?,

ix Sucrogen BioEthanol, 2012, Myths,

x SMH, 2013, Ethanol not the win for hip pocket it was made out to be,

xi Holden, 2012, Ethanol Innovation,

xii Department of Sustainability, Environment, Water, Population and Communities, Australian Government, 2012, Fuel quality standards: Overview,

xiii Department of Sustainability, Environment, Water, Population and Communities, Australian Government, 2012, Fuel quality standards: Ethanol Labelling Standard,

xiv Department of Sustainability, Environment, Water, Population and Communities, Australian Government, 2012, Fuel quality standards: Ethanol E85 fuel quality and fuel quality information standards,