Is e10 better than unleaded? Fuel economy, price and performance

We received a report on Twitter today showing e10 fuel being sold at a higher price than regular unleaded. This prompts the question, is e10 better than unleaded in terms of fuel efficiency, price and performance and at what point does the cost factor in? Are there any other considerations to using e10 fuel, such as environmental factors?

Help inform this thread and we’ll award some BS buster badges for your profile.

e10 priced higher than regular unleaded:


It appears to be a mixup in entering the prices.

Our local United prices E10 for 3 to 4 cents a litre less than U91

E10 needs to be around 3% cheaper than U91 to achieve the same running cost due to ethanol being consumed faster than petrol, thus resulting in reduced mileage.

P.S. It is Monday morning so that may explain the price board mixup.


I see @fred123 has beaten me to the post but I’ll join anyway.

e10 has 3-4% less energy per unit than 91, so should be priced 3-4% cheaper, all things being equal. United servos around Melbourne used to keep it 4c/l below 91, but it has crept up to 3c/l as the big players have started offering it, and seems they are increasingly pushing it.

This being a United servo sign begs whether as @fred123 posts, it is a genuine error, or the actual pricing.


e10 has a lower energy content that regular unleaded petrol, therefore vehicles using e10 will use more fuel (L/100km) than the same car running on unleaded fuel such as RON91. To offset the increased fuel consumption using e10, the cost of e10 would need to be around 3% cheaper to break even. The example in the original post, the e10 would need to be around $1.54/L to make it stack up economically.

In relation to the environment or reducing the volume of non-renewable fuel used by the same vehicle, there could be still a net saving in non-renewable fuel used when changing to e10. This could be around 9.7% in non-renewable fuel used. While this many not seem significant, if all of Australia’s car (most of the existing car fleet that can run on e10) there could be significant non-renewable fuel savings.

While this sounds attractive, one also needs to consider the source of the ethanol used in e10. Ethanol can be generated from food products or non-food products. It would be better for ethanol used to be from non-food products where its production also does not compete for food production agricultural land The reason for this is that if ethanol production competes with food production, there will be less food available for the planets population and it is likely to drive up food prices which it competes with.

The last factor is some recognised ethanol problems. If ethanol is used in a vehicle which is not compatible with ethanol, it can damage the fuel system (see if you can can run on ethanol here). E10 also has a scouring effect on the fuel system and poorly maintained vehicles it can result in blockages in the fuel filter. The last consideration is ethanol absorbed water and a vehicle not doing regular kilometres may have water buildup in the fuel tank resulting in the corrosion of the fuel tank/fuel system or can result in water coming out of solution and entering the fuel system causing poor running or the engine failing to ignite.


For all of the above reasons it makes little difference whether you choose E10 or not providing your car or mower etc has an engine able to use E10.

As noted there is a potential benefit to the environment in using ethanol when it is produced from a renewable resource such as sugar cane. However there is no price benefit. There is only a loss when using E10 based on typical SE Qld price differences of 2-3c per litre less for E10.

You might also need to fill up if using E10, 2-3 times more each year due to the lower energy content and approx 3% higher consumption compared to regular unleaded. This may depend on how low you dare to go on the tank! There is a cost in time, and use of E10 perhaps makes it more likely you might hit another high in the petrol price cycle? For some it might be an unlikely issue if you fill up the same day of the week, every week regardless. But such habits are likely not a cost decision.

Which it is better for the environment?
Clearing land including rainforest to produce more ethanol, (whether domestically, in Indonesia, Brazil etc),
returning low value agricultural land to forest or selected food production, and investing in alternate greener energy options.

There is an alternate viewpoint that E10 is more a token taken in good faith to support better environmental outcomes than a better fuel or the future solution to a low carbon future.

As an aside the maximum benefit of ethanol blends is achievable in engines designed specifically to run on a high ethanol content. Eg E85, or even pure ethanol?

Combining the use of ethanol fuel with higher compression ratios (than those common in everyday petrol engined motor vehicles) ethanol can also match or exceed regular unleaded for fuel economy. Note pure ethanol is a great racing engine fuel at RON 108.6 and has a history of use in motor sport.



There is yet another viewpoint that e10 got its legs mostly because of the corn farming lobby in the USA. Apologies for the US tax activist reference, but I believe it is close enough to correct that it is correct. Wherever goes the US the world tends to follow because of the overweighted US marketplace.


Is it that simple?

The dynamics of our agricultural industry would appear a little different.

There is a strong allegiance to cattle, cane and coal. As far as I can ascertain Australia has not in recent decades provided an agricultural subsidy directly for cropping to produce ethanol. Indirectly ethanol production has been supported by being Federal fuel excise tax exempt with a progressive increase planned over time. We produce less ethanol bio fuel than we import.

Imported biofuel! Yes we import more than we produce and the imports are taxed at full rate with no exemption.

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Interestingly, Brazil has been using motor vehicle fuel of up to 100% ethanol for many years, long before the E10 debate started in Australia.,and currently mandates a minimum of 25% ethanol,.

On a slightly different note, when I was at school, we would sometimes be at the speedway at the Cairns Showgrounds on a Saturday night, which consisted of mainly JAP bikes which were said to be running on Shell A, and the smell of the exhaust was unmistakeable.

When I was based in Townsville around 1970, a guy who was said to be in the army had a Mk2 GT Cortina which was highly modified, and it was said that it could only run on Shell A, and he rarely drove it due to the high fuel cost.

I saw it a couple of times on a Saturday night driving along Charters Towers Road and the smell was also unmistakable.

There also used to be claims that engines running on vegetable derived fuels had to also use vegatable derived oils for lubrication but I suspect that it was just another urban myth.

I have not been able to find any reference to Shell A but I presume it was a fuel with a very high or 100% ethanol content.

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I can’t answer that question but have noticed a few things.

  • Know what you are comparing. One of my local petrol stations sells a blend of Unleaded 94 and ethanol i.e. not directly comparable with 100% Unleaded 91.

  • Typically the signage says “up to 10% ethanol”. That’s pretty dodgy since it isn’t a commitment to have anything more than no ethanol (or perhaps even could have no ethanol).

  • There are plenty of non-car petrol-fuelled devices that say that they can’t use ethanol at all. So e10 definitely isn’t better for them. :slight_smile:


Shell aviation gas. Old school up to 115/140 rated for piston engined aircraft. Or Jet A-1 for non propeller heads. The world has moved on a little since then.


I top up with E10 occasionally to remove any water in the fuel system as the ethanol will mix with any water in the tank cheaper than anything else


True, water in the tank will mix with the ethanol in the E10 blend. My preference is to not not get water in the fuel tank in the first instance.

Secondly the best way to remove any quantity of water from the tank is to drain the bottom of the tank with the vehicle on level ground. Unleaded fuel and water do not mix and the fuel floats on top of the water.

Topping up with E10 if there is water in the fuel tank creates the risk the E10 having sucked up all the water will drop out of the blend and sink to the bottom of the fuel tank where it will remain. Of course it might not be in a hurry to do so and some might drop out elsewhere in the fuel system.

There may be no direct benefit in using E10 if there is no water problem in your fuel. Science and experience suggests using E10 if there is water in your fuel tank is not a great solution. It is high risk. Ask a boatie!

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Shell A was not avgas.

When we were teenagers with hotted up vehicles, we would add some 115 or 145 avgas to the tank, but avgas is just higher octane leaded fuel, and the exhaust fumes smelt nothing like Shell A which had a very distinct sweet smell.

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Nothing is usually simple, nor often possible to follow ‘the money’ from and to all the requisite sources. Some countries have greater economic dependence on foreign exchange, some (like the US) subsidise their farming industry in multiple ways from tax breaks to price supports to outright gifts that are not packaged as gifts, and so on.

The cynicism in me suggest at least a small part of our equation is that by ‘topping up’ domestic fuel with e10 (and beyond) the oil companies have more to export yielding dollars in pockets from profits and the meagre taxes they might pay, and corn farmers have ‘the customer’ so all is good.


What ever the reasoning behind the financial interests in blended ethanol fuel production, it would seem there is little cost benefit in it for the consumer.

E10 users get insufficient saving in fuel costs to offset the loss in economy (litres per 100km).

Non E10 users pay more fuel excise per km travelled due to the discounted fuel excise rate applied to ethanol?

This notes that in Australia road users who purchase regular unleaded or the higher rated premium fuels, have been subsidising the road users who choose the E10 blend.

Excise tax for ethanol at $0.081 vs gasoline at $0.412 per litre. Oct 2018.

Cynicism appropriate. :wink:


Apologies @Fred123. Perhaps my grey matter is a little off. Hope you find the answer you are seeking. It will be good to have this clarified further.

Traditional piston engine aircraft Avgas had a much greater TEL content compared to automotive fuel. TEL = Tetraethyl-lead. Aside from being toxic it is considered one of the compounds that contributed to a sweet smelling exhaust from the aircraft.

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But then we can keep on making more ethanol but we can’t make any more petrol.

Whether ethanol has any place as a transport fuel long term is unknown. Maybe it will all (ethanol, petrol, diesel, LPG) be replaced by the hydrogen economy.

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Yes, ethanol is certainly renewable and so we do need to further advance it’s use where fuel burning is necessary. Engine manufacturers also need to step away from using oil based fuels and it appears so far most have been hesitant, or appear to have been hesitant, to make all motor vehicles engines more alcohol fuel friendly and more fuel efficient. Both these would lead to a decreased need for X amount of fuel per kilometre and a somewhat more eco-friendly outcome. Completely avoiding burning carbon based fuels is the better aim, until then reducing non-renewables is a good step in the right direction.

The Chinese Tokamak achieved 100 million degrees sustained for 10 seconds late last year so maybe more a heavy hydrogen economy :slight_smile: Back to the Future DeLorean with fusion reactor isn’t perhaps so far away anymore as it once appeared. One fusion reaction and travel for your lifetime but then how to store the energy from that reaction for a lifetime of use?

I agree but there are other possible sources for ethanol production including food waste as you noted. USA produces a lot of it’s ethanol from corn, again it is a food crop but even worse it is highly subsidised too and so is an unrealistic cost to benefit analysis from the beginning. Ethanol is renewable in the sense it can be produced by means that do not need to use non-renewable resources. Would it achieve cost effectiveness without using non-renewables or subsidies? Until someone tries to see I guess it is hard to accurately answer either way.

Should we continue using it? It may become a preferred fuel for certain uses particularly if we stop burning oil based fuels. In the near Medium term I would hope we step away from burning carbon wherever it is possible to achieve that.


In the general sense yes, but still has some strings attached.

To be renewable, it assumes that the CO2 produced through its production and use is being recycled in the carbon cycle…that being, all CO2 is captured by plants.

The other issue is in Australia is ethanol is currently produced from wheat starch, grain sorghum and molasses. While could argue the later is good as it may reduce sugar available in the rest of the market place, the first two are foods and their use directly competes with the food industry. This does pose an ethical dilemma. Diverting wheat (starch) and sorghum to ethanol reduces food for human mouths. I am not sure if this is a sustainable solution if one wants to ensure that there is adequate food for the world’s population.

The third point is that these main inputs to ethanol production require signifcant fertiliser inputs. This places potentially additional demand on phosphorus which is finite and winnable resources quickly being depleted.

Preference would be ethanol from non-food products or waste to ensure its long term sustainability.


All good points but that still leaves it infinitely better than fossil fuel, which has exactly zero sustainability (although theoretically we might find a way to manufacture methane, and potentially even higher alkanes, that is economically viable).

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