E10. The Facts and More
  |  First Published: June 2011

What’s the real story behind E10 fuel and its effects on the boating angler? There is certainly a lot of misinformation out there and there is also a lot of good information. And if you decide that E10 fuel and your boat are not a good fit, how do you find service stations that sell simple unleaded fuel?

Read on and we’ll discuss the pros and cons of E10 fuel, show you how to find service stations that sell unleaded fuel and have a brief discussion on high-octane unleaded fuel and its benefits (or lack thereof) for your boat and motor.

Before we delve into this rich subject, I’d like to acknowledge that this article was the result of the industry helping me out a lot. Every engine manufacturer went above and beyond with their help in regard to research and information provided. Also, Gary Fooks, considered by many as the research expert for outboards in this field, helped enormously. To all, a special thanks.

With that said, let’s get into it.

E10: HOW Bad?

E10 is a blended ethanol fuel that reduces the amount of petrol in the fuel mix to around 90%. Ethanol is a by-product of broad-acre crop farming (especially sugar cane in Australia) and many years ago the powers that be introduced E10 or similar fuels.

On the surface this sounded fine, especially for the farmers who stood to make extra money from the same crop. However, their advice did not take into account the recreational boating market and the effect E10 has on fuel storage components and the fact that E10 will separate into ethanol and unleaded petrol if exposed to moisture or condensation.

So now the boating public has reduced options on where to buy appropriate fuel, or is being forced to buy premium, high-octane unleaded petrol that really benefits only larger, high-performance outboards that were built in the past five years or so.

It has even forced many boat owners to evaluate their current fuel storage and delivery systems, in some cases leading to very expensive retrofits replacing existing components.

Q and A

1 My outboard manufacturer says my engine will cope with E10, so there’s no problem?

If your outboard manufacturer confirms that your engine is built to standards required to accept E10 type fuels then you should not have any problems as far as your engine itself is concerned. But, and this is a very big but, you need to ask yourself if your boat is ready. By this we mean, do you know if the fuel tank, fuel lines, seals, primer and filter are all E10 ready? If not, find out immediately because E10 damages fibreglass and aluminium tanks and melts many of the hoses and fuel system components. These dissolved components pass through the best filters and are deposited inside engines and have been shown to destroy expensive engine components. No engine warranty will cover the sort of damage experienced from this.

2 Ethanol boosts octane, so my engine will go better and/or faster.

High-octane fuel, no matter how the octane is boosted, won’t do a thing for your engine unless it has been designed to take advantage of high octane. That means that high-octane fuels (especially E10 and higher octane unleaded, like Premium 95 and 98) usually require a high compression engine to make any difference. There certainly are engines on the market that will undoubtedly perform better with higher-octane fuel but most mainstream outboards give little advantage to the user in terms of performance or fuel economy from high-octane fuel. A fact box hereabouts looks at high-octane fuel and some engines that are designed to take advantage of it.

3 V8 racing uses ethanol so it must be great.

V8 racing was under pressure to become more environmentally responsible and converting to E85 (85% ethanol) was as much a PR exercise as it was an environmental solution. These high-performance cars now have a shorter range with more fuel stops because they don’t get the same mileage from E85 as they did from regular unleaded petrol. The same has been shown to be true for outboards running E10, because E10 has about 3% less energy than regular unleaded petrol.

4 E10 is 3c a litre cheaper, so why not buy it?

Most petrol companies charge less for E10 fuel but the difference in price between standard unleaded and E10 varies widely. Another factor to consider is that E10 has 3% less energy per litre, which gives about 3% less range. For example, if fuel is $1.40 a litre then E10 needs to be 4c a litre cheaper JUST to break even in terms of kilometres per litre obtained. You end up paying more for E10 because you use more over the long term.

5 E10 is better for the environment.

Yes, but the jury is out on that. E10 is renewable because it comes from crops and not oil fields but the energy and effort needed to make the ethanol in E10 may well outweigh the environmental benefit. There is also the impact of increased pesticide, fertiliser and other chemical use to consider, something rarely mentioned. E10 will reduce some emissions, important in crowded cities, but it uses a lot of fuel, energy and pesticides to produce – not so good for our marine and coastal environments because most of the pollutants get washed into the rivers and creeks during rain.

6 There is an additive that will fix any problems with E10.

No additive claims to fix paint peeling, melting fibreglass or phase separation of ethanol and unleaded in stored or moored boats. All the claims made by these expensive additives are necessarily vague and we suggest that the buyer beware.

7 If E10 wrecks my boat can I claim for the damages?

The Qld and NSW governments have warned against E10 use in boats. So has BP (a sticker on every pump) and others as well, along with the odd boat manufacturer. Your chances of winning a legal or insurance claim from damage caused by E10 fuel to your boat fittings or engine are next to nil – you have been adequately warned.

8 I’ve heard about phase separation. What is it and can’t I just shake up the petrol tank to remix it?

Phase separation is a most serious issue and commonly occurs when E10 fuel is left to sit idle for an extended period and moisture has entered the fuel system. Phase separation is when the ethanol and unleaded literally separate from one another in the presence of water, creating two layers of different fuels. No amount of shaking, mixing or magic additive will blend the two back together. They are like oil and water once separated.

Ethanol is heavier than unleaded petrol and sinks to the bottom of fuel tanks. This is all fine while the unleaded fuel is running through the motor, although motors will typically underperform because the octane level of the unleaded fuel is lower than it should be. Serious issues occur once the highly reactive ethanol enters the motor and is run through fuel system components such as hoses and filters that can at best cope with 10% ethanol. You think E10 is a good solvent, try almost 100% ethanol! This is why most motor manufacturers advise against using any ethanol fuel, and certainly not blended fuel that has undergone phase separation.

Bigger, Bigger

As I was researching this article and reading reams of interesting and frightening reports, it occurred to me that the E10 issue is much bigger than I first imagined.

A quick overview shows some alarming points that boat owners, boat manufacturers and boat users really need to get their heads around.

Starting at the top, with ethanol being such a good solvent.

The nature of ethanol means that it is a stronger solvent than ordinary fuel. This may lead to particles in your fuel storage system and fuel lines being dissolved, loosened or disturbed, allowing these particles to enter the fuel destined for your engine. At best, your fuel filter catches the dissolved particles; at worst, they make it into your engine and start to accumulate in all sorts of strange places.

Ethanol can also damage gelcoat and fibreglass around fuel intakes. The Queensland Government advises boaters to clean up ethanol blended fuels spills immediately and thoroughly!

But it gets worse. Aluminium fuel tanks and boats are at risk due to ethanol’s ability to conduct electricity. The extra conductivity of ethanol can lead to an increased risk of galvanic corrosion, reducing the structural integrity of fuel tanks and boats, and promoting unsightly corrosion blisters under paintwork, especially near the fuel inlet.

The very worst are fibreglass tanks. If they were not built to E10 standard, any ethanol will immediately start to dissolve the tank. That means a weakened tank that has the potential to fail and leak. But before then, the dissolved fibreglass chemicals, like styrene, will pass through the best of filters and coat the inside of sensitive engine components. This has led to engines being damaged beyond repair.


Some say a week is about long enough to store E10 in a warm environment. Others say two weeks, while others refuse to speculate. I work in the rec fishing industry and I can say for a fact my boat does not hit the water every week and I guess other most boats don’t, either. So the fuel is likely to go off and lose its octane rating, leading to engine pinging and underperformance.

Tips for storage of E10 include completely emptying fuel tanks or using a fuel stabiliser. So just how do you go about removing all the fuel from your in-built tank? Fuel stabilisers are great as long as the stabiliser is added to new fuel; they will not stabilise old fuel or rejuvenate old fuel.

Yet more problems arise if your tank is almost empty when stored, even for a short period, because it leaves more air space in the fuel tank for water vapour condensation to occur, leading to phase separation of the E10 fuel.

To stop phase separation it is recommended to fill the fuel tank almost to the top to reduce condensation. Fine, but then the E10 fuel will go off if left to sit for two weeks. And fuel also expands with heat, and you do not want E10 fuel leaking from the fuel vent onto your boat. A no win situation.

So is it any wonder that all fuel sellers in Australia have warnings about the use of ethanol blended fuel in boats? It’s a warning boaties should heed.

What to do

For starters, the easiest way to avoid the problems is to not use E10 fuel for your boat – ever! E10 really is a bad idea for boaties.

Failing that, and at times you may not be able to avoid E10, you should completely drain the fuel tank and mechanically clean it to remove any traces of rust or aluminium oxides and then dry it thoroughly to minimise the presence of water.

If your boat was built pre-1990, seriously consider replacing the fuel tank, fuel line and components and get a fuel filter that is at least 10-microns. And carry spare fuel filters and change them every three to six months.

Just about all outboard manufacturers recommend that a fuel stabiliser should be used (regardless of the fuel) to ensure the fuel does not lose its octane rating. A lowering of the octane rating in your boat fuel will lead to a host of problems with performance.

Several manufacturers say, though, that these fuel stabilisers will not fix phase separation or increase octane levels of old fuel and should be added only to fresh fuel.

If you must use E10 fuel, it is highly recommended to fill your tank to around 90% of its capacity, leaving as little air space as possible. It is not recommended to completely fill the tank because expansion of the fuel when heated through the day will lead to leaking from the overflow or fuel vent, exposing your fibreglass or aluminium boat to the dangerous E10 fuel. Again, another compromise you must make with E10.

So there are a few tips and tricks if you have to use E10. But make no mistake, the whole industry recommends you DO NOT USE E10 fuel for boating purposes unless you absolutely must.

I hope this has helped you make some sense of the E10 debate. Boat manufacturers, component distributors, outboard importers and distributors are all working hard to make products that will be capable of dealing with E10’s limitations in a marine environment. But not one of them can solve the big issues of phase separation and fuel going off in such a short period.


Outboard Manufacturers say:

Evinrude: Evinrude motors can tolerate up to 10% alcohol in fuels.

Honda: Honda engines are designed for good performance using petrol containing up to 10% ethanol.

Mercury: Mercury engines will withstand up to 10% ethanol in fuel

Suzuki: Recommends the use of pure petrol without ethanol, but can use up to 10% ethanol if necessary.

Tohatsu: Recommends use of fuel up to only 10% ethanol. Use of fuels with more than 10% ethanol voids the warranty for all alcohol-fuel related malfunctions.

Yamaha: All 2008 and later models are suitable for use with E10 blended fuel. Models prior to 2008 are not suitable for Ethanol blended fuels.


Check your components

E10 fuel is a hull/fuel system issue, not just an engine problem.

Queensland-based The Haines Group (Signature, Traveller and Seafarer boats, Suzuki outboards) are right on the ball.

CEO Greg Haines said, “We have been well aware of the challenges of ethanol fuels and especially their effects on GRP (fibreglass) hulls. By late 2009 we had abandoned fibreglass fuel tanks and changed over to moulded plastic tanks with E10 resistance. At the same time we verified that the fuel hoses and fittings on every one of our boats was manufacturer-specified to withstand E10 fuels.

“Even so, we are concerned about phase separation and short fuel life so we don’t recommend E10 for any of our boats. That’s in line with the warnings of fuel companies and state governments.”

The Haines Group boats now have a warning on every new boat’s fuel filler stating that E10 is not an option.

Before you buy a new or second hand boat, take a moment to consider its suitability to E10 fuels.


Fuel Stabilisers

Fuel in the can or in the engine fuel tank starts going stale immediately, resulting in hard starting, poor performance and reduced engine life.

Fuel stabilisers aim to keep fuel as fresh as the day it was bought. That basically means the stabiliser will maintain the octane rating of the fuel but most stabilisers also inhibit moisture uptake, which is a very handy extra result if you were to use E10 fuel accidentally or deliberately.

There are many brands of fuel stabilisers in Australia. Here are some recommended by the outboard industry for use in Australia.


Marketed for over 40 years in the US, STA-BIL is recommended by more than 100 engine and equipment manufacturers. The manufacturer states STA-BIL is safe to use in any petrol engine and will not harm any engine or fuel system components or catalytic converters.

When added to fresh fuel, STA-BIL stops the formation of gum and varnish in fuel system components. It contains corrosion prevention additives to fight the damaging effects of ethanol in fuels and cleans fuel injectors and carburettors restoring performance. Honda Australia uses STA-BIL products to maintain their fuel and recommend it to their customers.

• Yamalube Fuel Stabiliser & Conditioner Plus

Yamaha strongly recommends Yamalube Fuel Stabiliser & Conditioner Plus for anyone using E-10 fuels. The alcohol-free formula helps prevent fuel oxidation and phase separation from moist, rich air. When used continuously, it keeps fuel fresh, potent and free from gum and varnish for up to one year of storage. Its metal filmers provide extensive protection for steel and aluminium components. This product is available in 385ml and 946ml bottles from retailers of Yamaha products.

• Mercury Quickstor

Added to fuel before storing or when the engine is not being used for extended periods, Mercury Quickstor prevents regular and ethanol-blended fuel from breaking down and oxidising.

Mercury Marine recommends boat owners buy fuel only from trusted sources, routinely inspect fuel tanks for water sediment, regularly check their fuel filters and carry a spare fuel filter in case of sudden blockage. One bottle of Mercury Quickstor treats 227L of fuel and is available widely at many boating outlets and chandlery stores.


High-octane (premium) fuel and outboards

Higher octane ratings correlate to higher activation energies . Activation energy is the amount of energy necessary to start a chemical reaction. Since higher-octane fuels have higher activation energies, it is less likely that a given compression will cause autoignition.

It might seem odd that fuels with higher octane ratings are used in more powerful engines, since such fuels ignite less easily. However, an uncontrolled ignition is not desirable.

A fuel with a higher octane rating can be run at a higher compression ratio without causing detonation. Compression is directly related to power and to thermodynamic efficiency, so engines that require higher octane usually deliver more power and do more work for a given energy unit of fuel. Engine power is a function of the fuel, as well as the engine design, and is related to the octane rating. Power is limited by the maximum amount of fuel-air mixture that can be forced into the combustion chamber . When the throttle is partially open, only a small fraction of the total available power is produced because the manifold is operating at pressures far below atmospheric. In this case, the octane requirement is far lower than when the throttle is opened fully and the manifold pressure increases to atmospheric pressure, or higher in the case of supercharged or turbocharged engines.

Many high-performance engines are designed to operate with a high maximum compression, and thus demand high-octane, premium fuel. A common misconception is that power output or fuel mileage can be improved by burning higher-octane fuel than a particular engine was designed for.

The power output of an engine depends in part on the energy density of its fuel, but similar fuels with different octane ratings have similar density. Since switching to a higher-octane fuel does not add any more hydrocarbon content or oxygen, the engine cannot produce more power. Therefore an engine specifically designed to take advantage of high-octane fuels is necessary to get the most from their use.

There are few outboard motors in Australia that can really take advantage of high-octane fuel. Preliminary research shows that it is only the high end of the market where boaters can take advantage of high-octane fuel, regardless of the claims made by the fuel providers.

Two models have the ability to use high-octane fuel to its maximum: Mercury 250hp Pro Verado and Mercury 300hp Pro Verado. Both these engines have been designed to provide the high compression rates needed to maximise the extra octane levels in Unleaded 98 and others. This is a very important because many fuel outlets now supply only Premium (high octane) and E10. Unless you have specific information from the engine manufacturer that your outboard will perform better on premium fuel, there is absolutely no need to use it unless your only other choice is E10, which should be avoided at almost any cost.


Finding Fuel


Simply follow the link, click on the unleaded fuel button and then search. This will bring up all Caltex stations with unleaded fuel in Australia. You can zoom in to any area you are interested in.www.nowwhere.com.au/caltex/austlocator/caltextripplanner.aspx


Follow the link below and you can download the entire list of all Shell service stations all what they offer, including fuel types, restaurants, toilets, showers and more.



With this link you need to type in a suburb, click on ‘advanced search’ and then select ‘Unleaded 91’ to find outlets that sell unleaded fuel. To make the list a little more refined you can choose to locate the 20 nearest stations or the 10 nearest stations to the suburb of your choice.


You can do a trip plan and do an advanced search, clicking Unleaded 91 and so forth. This will give you a route to follow plus if you click on the numbers on the screen you will have all the information pertaining to that service station available in a pop-up box.


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