Article written and reproduced with kind permission of the author, Chris Thompson CAE Eng Tech AMIMI, and the Stag Owners Club.
The issue of Ethanol blended with petrol You may or may not be aware that the majority of petrol sold at the pumps in the UK now has a blend of 5% Ethanol mixed with the fuel. This is set to increase to 10% Ethanol from 2013. Despite being hailed by some as a greener alternative to pure crude oil derived petrol, ethanol is not without its drawbacks when used in vehicles that were not designed with this fuel in mind. There are many different problems that have been identified with the use of ethanol as a fuel. By grouping these issues together I hope you will gain a better understanding of the problems now faced by motorists.
What is Ethanol? There is no magic alchemy at play here. This is not like the discovery of nylon that allowed scientists to invent something that would revolutionise our world. Ethanol is simply a form of alcohol modified to use it as a fuel by making it undrinkable (ethyl alcohol). Its chemical formula is C2 H5 OH (often simplified to EtOH). Ethanol is made by fermenting and distilling starch or sugar crops such as sugar cane, sugar beet, wheat or other grains…in fact pretty much any fruit and vegetable matter or waste.
This is not a new discovery. Human beings have been distilling alcohol for thousands of years. Residue found on pottery from China dating back 9,000 years imply that Neolithic people consumed alcoholic beverages.
Ethanol was first prepared synthetically by Henry Hennel in Great Britain and S.G.Serullas in France in 1826. Ethanol was used as a lamp fuel in the USA as early as 1840 but a tax made on industrial alcohol during the American Civil War made its use uneconomical. The tax was repealed in 1906 and the original Ford Model T ran on ethanol until 1908. Henry Ford said it was the fuel of the future (that statement may still be true, but I’ll come back to that later). Ethanol was widely used as a fuel for automobiles in the USA until the advent of prohibition in 1920 when ethanol sellers were likened to ‘moonshiners’ and the fuel fell out of favour.
The discovery that adding Tetra-Ethyl Lead to petrol significantly improved its octane rating saw ethanol being pretty much ignored a motor fuel for many decades. Pure Ethanol has an octane rating of 113 endowing it with a far higher resistance to knocking or pinking than hydro-carbon fuel, indeed this explains why another version of alcohol (Methanol) has been used to fuel highly tuned dragsters and some very high performance racing cars of the past.
Why Ethanol is making a comeback? The European Union has decreed (under the guise of The Renewable Transport Fuels Obligation “RTFO”) that fuel companies are obliged to include 3.5% bio fuel in all their mineral petrol and diesel sales. There is no specific mandate as to the percentage in each individual fuel and so up until recently the oil companies have focused on adding a greater percentage of bio fuel to their diesel and leaving petrol alone completely. This is because it is relatively easy to make bio diesel and has few if any detrimental effects on the vehicles using it (Bio diesel does not contain ethanol). However the amount of bio fuel that must be included in fuel sales goes up by a small percentage each year and the fuel companies now have no choice other than to have a renewable element to their petrol.
Compatibility with fuel system materials Ethanol may have the dubious virtue of being a renewable energy source (which is good news if the machine using it has been specifically designed to use this fuel) but unfortunately a less desirable quality of the fuel is its corrosive nature. This is partly due to the high oxygen content. Oxygen is a very active element…in fact it reacts with almost everything. It is oxygen that turns iron into rust amongst other things. In liquid form these reactions are accelerated (consider how much quicker metals corrode in water compared to the air) and when mixed with hydro-carbon fuel, unexpected issues have been identified. Ethanol is also acidic, and this acid damages many materials.
Starting at the beginning where the fuel is added to the vehicle…the filler neck of the fuel tank is attacked. In older vehicles this often has a rubber connection. Natural rubber is quickly broken down by Ethanol. A well-known motoring organisation noticed a worrying trend involving the filler neck of a certain popular air-cooled German camper vehicle. The rubber pipe would perish allowing fuel to leak during re-fuelling and petrol smells emanating from the vehicle. When a new pipe was fitted it also would perish within six Months.
Moving on to the fuel tank. Many older fuel tanks are made using two sheets of pressed mild steel welded together. A sealant is used to ensure a perfect seal (unlike water, petrol has no surface tension and will leak through the tiniest of gaps). Ethanol will react with this sealant releasing it as a gooey substance into the fuel. Instances have been found of fuel tanks that have been efficiently sealed for decades being damaged by Ethanol in petrol. Even the metal itself is not safe. Hydrogen bonding causes Ethanol to be hydroscopic to the extent that it readily absorbs moisture from the air. In a humid country like Britain this equates to a significant amount of water being added to the fuel and the steel (which has now had its protective layer stripped off by the Ethanol) begins to oxidize (rust).
Ferrous metals are not the only ones to be adversely affected by Ethanol. Copper fuel pipes, brass fittings etc are also corroded. Moving parts in fuel pumps (including rubber diaphragms if they have them) are damaged. Fuel filters are rapidly blocked by the residue of all these reactions. Rubber petrol pipes will break down and crack leading to fuel leaks. Carburettors and the jets inside them are also corroded by Ethanol. Ethanol also attacks cork (often used as a gasket in older carburettors). Below is a list of materials known to be damaged by Ethanol…the list is not exhaustive.
Zinc and galvanised materials, Brass, Copper, Terne plate (lead/tin coated steel), Aluminium, Magnesium alloys, Zamak 5, Polyurethane, Polymers containing alcohol groups, Fibreglass-reinforced polyester and epoxy resins, Shellac, Acrylonitrile butadiene styrene (ABS), Polyvinyl Chloride flexible version (PVC), Natural rubber, Polyethylene Terephthalate (PET), Cork, Petseal, Nitrile rubber (NBR) [Buna N] with low acrylonitrile (CAN) content, Viton A, Polyamide 6 (PA 6) [Nylon 6], Polyamide 66 (PA 66) [Nylon 66].
It has been suggested that only older vehicles are likely to suffer negative reactions to low percentage Ethanol content in fuel, however extensive research has discovered that some GDI (Gasoline Direct Injection) engines produced as late as 2007 have materials in the fuel pump that will be damaged by Ethanol.
There is another corrosive reaction to be taken into consideration. That of Galvanic corrosion. This occurs in fuel systems containing electronically dissimilar metals in the presence of petrol and alcohol fuels (eg, carburettors containing brass and zinc components). Adding corrosion inhibitors to the fuel will undoubtedly help this situation but modification of carburettors using more corrosion resistant (and expensive) materials is expected. Most carburettors are made from an alloy (Zinc/Aluminium etc…) the jets in the carburettor are normally made from brass. These metals are electronically dissimilar, however hydrocarbon petrol is a poor conductor of electricity and therefore galvanic corrosion is negligible. Ethanol however is a fairly good conductor of electricity (about the same as water) and it is this property that has lead to previously unaffected components suffering from this type of corrosion.
Blending Ethanol with the petrol is the final act that the fuel company undertake. It is added only when the fuel is in the tanker, ready to be delivered. This is because if added sooner than this, the Ethanol would attack the storage tanks in the fuel depot. It is for this reason also that Ethanol can’t be transferred along piplines with the rest of the fuel (it eats them too). It has also been known to damage the storage tanks in service station outlets and these need to be modified to contain Ethanol fuel.
Drivability Issues There are a great number if issues to be considered here that affect the drivability of vehicles using fuel containing Ethanol. Some are easier to understand than others. Let’s start with the basics…
The ideal fuel/air ratio for a petrol engine (Stoichiometric Air/Fuel Ratio) is between 14.5 & 14.7 to 1. That is 14.7 parts air to 1 part fuel by volume. For pure Ethanol this ratio is between 8.9 & 9 to 1. (9 parts air to 1 part fuel).
This can partly be explained because Ethanol contains 35% Oxygen by weight and therefore will naturally ‘lean-off’ the fuel/air mixture.
Even at only 5% mixture, Ethanol will alter the correct fuel/air ratio and lead to unadjusted engines running weak. (As a very crude guide…slightly rich mixtures will result in wasting fuel. Slightly lean mixtures can result in significantly increased combustion temperatures.) To further add to the problem, vaporisation can lead to incorrect fuel metering and a further ‘leaning’ effect (Enleanment). It should be noted that an increase in combustion temperatures will not necessarily register on the vehicle’s temperature gauge. This gauge predominantly operates via a sensor in the cooling system (usually in the cylinder head) and records the temperature of the coolant directly in contact with the sensor. This is usually accurate enough to indicate if the engine is operating within its design temperatures. Permanent damage may already have occurred to valves and pistons before any change is noticed in coolant temperature.
Even modern engines using electronic fuel injection systems can be susceptible to this phenomenon. Most modern vehicles use a ‘closed loop’ system to maintain and monitor perfect fuel/air ratio (Lambda 1). This is achieved by the use of an Oxygen (or Lambda) sensor in the exhaust. This is active under idle and light cruise conditions, however under heavier load conditions (WOT ‘wide open throttle’) the system reverts to open loop and relies on the map in the engine ECU. It is unlikely that under these conditions even a modern engine will be able to compensate for the necessary change in fuel/air ratio required when using a fuel other than 100% petrol. Any pinking or knocking caused by a lean mixture may be detected by a knock sensor (if fitted) and lead to reduced engine power and possibly illuminate the M.I.L. (Malfunction indicator lamp) depending on the sophistication of the engine management system. Some manufacturers already produce vehicles that can run on fuel with as much as 85% Ethanol mixture (E85) proving that Ethanol is suitable as a fuel for internal combustion engines provided that it is designed with this fuel in mind but it is unlikely that carburettored vehicles or those fitted with mechanical or early electronic fuel injection will be able to make sufficient adjustment to the mixture strength while running on E10 (which will be here in 2013).
Another issue that has been identified is cold weather drivability (CWD) including reluctance to start. Tests conducted on a variety of vehicles using E5 & E10 fuels have recorded stalling problems at idle, difficulty in starting, hesitation and flat-spots, carburettor icing and loss of power. Some vehicles are far less prone to these faults than others (predominantly, the newer the car, the less likely it is to suffer ill effects).
Carburettor icing typically occurs in cool and humid ambient conditions because of a reduction in temperature caused by vaporisation of the fuel. This results in the air temperature falling below its dew point and the moisture it contains condenses and freezes to the carburettor components. The depositions of ice on components restrict air flow resulting in loss of power or stalling. The exact conditions under which carburettor icing becomes an issue depends on the vehicle design and fuel quality but as an approximate guide the problem potentially occurs between -3 and 12 Centigrade (below -3 there tends not to be enough moisture in the air).
In theory adding Ethanol to petrol should decrease the risk of carburettor icing (aviation fuel uses alcohol to reduce carburettor icing issues) but tests conducted in Australia and in the USA contradict this with the opposite seeming more likely to occur (I told you some things were harder to understand than others).
Ethanol has a higher volatility than petrol and therefore is vaporises more readily. This can lead to ‘vapour lock’ in components such as carburettors and fuel pumps etc, particularly if allowed to heat soak. This means that a hot engine that is switched off will heat soak the fuel (which it does anyway) and cause starting problems if the engine is restarted whist still hot. Some vehicles may suffer from vapour lock whilst running, especially on hot days, leading to loss of power and cutting out.
A study conducted in Australia by the Orbital Engine Company identified the formation of heavy deposits on inlet valves in some vehicles. The extent of the deposits was such that they had ceased to rotate. It was believed that there was potential for these deposits to fall off and become trapped between the valve and seat leading to loss of compression. It is unknown if this condition would occur in the UK as inlet system detergency additives have been in use here for many years.
Orbital also reported increased deposit formation on piston crowns and piston ring grooves in some vehicles. This could increase the risk of spark knock or pre ignition and more seriously, increase the risk of engine failure due to piston seizure.
Health and Safety There are a number of issues that directly affect the health and safety of us all. Not least of which result from the increased risk of fuel leaks. The more rapid deterioration of fuel pipes for example could easily result in petrol being sprayed onto a hot component such as the exhaust manifold. The leaning effect of Ethanol could lead to engine failure (not a comforting thought in lane 3 of the motorway). Engine malfunctions caused by the incorrect metering of fuel due to Ethanol also increase to production of ‘oxides of nitrogen’ (NOx) in the exhaust fumes. I’ll spare you the chemistry lesson, but Nox is nasty stuff.
We are all familiar with the expression ‘carbon footprint’. There is no question that new vehicles have a lower carbon footprint (once they’ve been built) than old ones. However the biggest carbon footprint a car ever makes is during its construction. Prematurely removing older cars from the road may sound like a green idea (and if it’s a rusty old banger then is probably is) but a well maintained old vehicle will overall have a lower detrimental effect on the environment than replacing it with a new car for no other reason. Likewise having to manufacture replacement components for said cars due to the ravages of Ethanol will also increase carbon emissions, which is the exact opposite of the intended goal.
Number of vehicles affected A government report concluded that based on age approximately 8.6 million vehicles will be unable to run on E10 fuel in 2013 when E5 fuel is phased out. In addition to this many thousands of relatively new first generation GDI powered vehicles and motorcycles will be unable to run on this fuel. Based on an average life of 13 years it is expected that approximately half of these vehicles will still be in use when the introduction of E10 fuel takes place.
This report also concluded that “Consideration should be given to maintaining a specification for E0 fuel for historic and vintage vehicles.”
It is gratifying to learn of this final recommendation as it appears to be the only one that understands that historic vehicles will not simply ‘go away’ as all the other reports seem to conclude.
Recommendations Although it may seem to be the case, the introduction of Ethanol into petroleum spirit was not intended simply to attack motorists and destroy old cars. There are most definitely arguments to support finding alternatives to our dependence on fossil fuels. Engines and fuel systems can be designed to run on various blends of Ethanol fuels. The Ford Model T did that more than 100 years ago. Speaking of which, if you remember the quote from Henry Ford that Ethanol was the fuel of the future? Well perhaps it is…but is it the fuel of the present? That is the question. For many of us the answer is no. This is because our vehicles were designed to run on a particular type of fuel, and if we use an alternative fuel then there are consequences to this (you wouldn’t expect a petrol engine to run on diesel or paraffin).
In the UK there is no requirement to display the content of Ethanol in petrol, so you don’t know what you are buying…this is not acceptable. Let’s be clear on one thing…the big fuel companies are not the bad guys here. They must comply with regulations. But there are things that we can do. I would urge everyone to write to their MP and ask that the following points be raised in Parliament.
1. That fuel pumps are clearly marked to indicate the Ethanol content of the fuel they dispense (E0, E5, E10 etc…)
2. That information pertaining to the effects of Ethanol be made freely available via a website (this will have a practically negligible cost to the taxpayer).
3. Most importantly, that the fuel companies are given the ability to continue to supply an amount of E0 fuel for the foreseeable future.
We need to make this an issue for the Government. The rising cost of fuel is already a major problem for many of us, but to pay so much for fuel that is destroying our cars is unfair. By allowing a percentage of E0 fuel to be available, this will address the issue for the owners of older vehicles. Newer vehicles will be able to run on Ethanol blended fuel and by the Governments own figures, the number of older cars will reduce each year and more and more vehicles will be able to use Ethanol fuel.
As Ethanol is only added in the final stage of fuel distribution this is easily possible. I have contacted the major fuel suppliers and asked them directly about the addition of Ethanol in the petrol they sell. The results vary, but generally speaking…Super Unleaded fuel is far less likely to have Ethanol blended into it than standard Unleaded. But this will change as the regulations force the fuel companies to increase the amount of bio fuel they sell. (This information was correct at the time of asking…Feb 2011)
BP Ethanol is added at 5% to unleaded petrol at all sites across the UK. BP Ultimate (super unleaded petrol) does not have Ethanol added, except in the South West of England.
Esso Ethanol is added at 5% to unleaded petrol at most sites in the UK. Esso Super Unleaded petrol does not contain Ethanol, except in the South West of England (Devon & Cornwall)
Shell Shell has repeatedly refused to answer the question. It is therefore an assumption only, that all Shell petrol should be considered to contain 5% Ethanol.
Texaco Ethanol is added at 5% to unleaded petrol. Texaco Super Unleaded petrol does not contain Ethanol.
Total Ethanol is not added to any Total fuel (including standard unleaded petrol). Except in the North West and South East of England.
Total have kindly provided a list of filling stations where E0 petrol can still be purchased. Click this link to download the list TOTAL E0 Fuel Sites.xls
As far as I can gather, the only reason that the super unleaded fuels seem to be ethanol free is because it is harder to obtain the fuel quality required for super unleaded if Ethanol is present. However several of the oil companies told me that this will change in the future but that no date has been set.
Chris Thompson CAE Eng Tech AMIMI