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December 13, 2016



Ethanol in Motor Gasoline

Eat it, drink it, or burn it as fuel?

By Kevin Cameron December 1, 2016


The introduction to a book on bartending once began, referring to ethyl alcohol, “Mankind has been systematically poisoning himself for 50,000 years.” To this we can add the present controversies over E15 and higher-percentage gasoline-ethanol blends. Plastic Ducati gas tanks have absorbed ethanol sufficient to swell, making it almost impossible to free them from the frame rails. Plastic or rubber fuel system parts can do the same, causing carburetor or fuel quantity floats to sink and possibly resulting in leakage. Upon removing carb float bowls, we may find sludgy green deposits. Operators of passive-fuel-system engines (those that cannot automatically adjust their own mixture) say they’ve had “ethanol lean-out”, leading to overheating and seizure. How? Ethyl alcohol contains only 2/3 as much energy per gallon as gasoline hydrocarbons do, so the more alcohol you add to motor gasoline, the leaner your mixture becomes. With E10, the lean-out effect is 1/3 of the 10% ethanol, or 3.3% - easily covered by the safely rich condition of most street-operated carburetion. Carburetors had to be set rich enough to be safe in the coldest anticipated conditions (air density increases but fuel density remains constant, which is a lean condition), so they operated comfortably rich in warm weather.

But with E15 and higher levels of alcohol addition, the percentage of lean-out becomes greater and the cooling effect of excess fuel is lost, causing combustion temperature to rise. This is the problem of carbureted engines run on E15 and higher.


Clearly, if E15 is a pump option only, the buyer can take care to select a fuel safe for his/her vehicle. But a fear exists that availability of E15 signals a Federal trend away from fuels (E10) that are relatively safe for engines with passive fuel systems. This would imply a future in which such vehicles could be operated only on expensive specialist fuels such as racing gasoline.

There are limits to ethanol use even in the case of fuel injection. As we add ethanol, the mixture leans, but the oxygen sensor in the exhaust detects the change and enriches the mixture in proportion. Sounds good – where’s the problem? The problem is that vehicle makers size their fuel injectors for the anticipated fuel. If the fuel changes so that greater volumes must be injected, eventually the flow limit of the injector is reached. Beyond that point, the oxy sensor, computer, and fuel system can no longer keep up with the drop in fuel energy as we add more and more ethanol. Again, the result is enleanment. To cover this possibility, vehicle manufacturers generally forbid the use of alcohol blends higher than E10.

Some vehicles are not limited in this way – the so-called ‘Flex-Fuel’ vehicles. Their fuel systems are designed to be able to cope with high-alcohol blends such as E85. The added cost of this fuel flexibility is buried in the generally higher price of such vehicles. As you may have noticed, Flex-Fuel vehicles are often large. Normally, if a maker wants to produce a high-profit luxury SUV which uses twice the fuel of the usual econobox, it must comply with CAFÉ standards (CAFÉ = Corporate Average Fuel Economy) by producing a great many more economical vehicles so that the average economy of that maker’s fleet averages out to meet the standard. But a deal was made; if the heavy vehicle was built as Flex Fuel (making possible operation on lower-emissions alcohol-rich blends such as E85), then 100 such heavy vehicles could legally be counted as a smaller number. Who could resist?

But wait – how did we get into adding ethanol to motor gasoline in the first place? Back in the late 1970s and early ‘80s there were hundreds of thousands of old carbureted vehicles on the nation’s highways. In their carburetors, fuel metering needles and the orifices in which they operated had worn in use, making fuel mixtures richer and increasing emissions of unburned hydrocarbons. Was there a way to fix this? Yes there was – to dilute motor fuel (especially in smoggy urban areas) with a low-energy-content ether – MTBE. Thus began the use of so-called “oxygenated fuels”. What this term actually means is that such fuels are partially burned (that is, partially combined with oxygen), somewhat reducing their content of chemical energy.

The MTBE program began with great enthusiasm and purpose, constructing specialized plants for making the stuff. Then came a terrible blow; MTBE was not decomposed by soil bacteria as normal fuel hydrocarbons were. It persisted in ground water for long distances, appearing in drinking water. Screech, the MTBE program was quietly halted. In its place was put ethyl alcohol.

Ethanol is an excellent fuel which strongly resists detonation. The power gain achieved on 100% alcohol (which has long been used in Australian motorcycle racing) comes not from its energy content, which is low (see above), but from its high heat of evaporation. As alcohol evaporates, it takes heat from the air with which it is mixed, refrigerating that air and increasing its density such that a greater weight of fuel/air mixture will fit into engine cylinders.

Although alcohols cause slow swelling of the familiar plastic ‘Plexiglas’, they are listed as very compatible with nitrile rubber, a common seal material. This apparent easy solution is denied us by the fact that gasolines now contain large percentages of aromatic compounds (toluene, xylene, xylidene) which are not compatible with nitrile rubber. Choice of fuel system elastomers is tricky.

Further, quoting from the Owen and Coley “Automotive Fuels Handbook”, “Methanol and ethanol are corrosive to many of the metals that are used in conventional fuel systems such as terne plating used in fuel tanks (a lead/tin coating on steel), aluminum, copper, brass, magnesium and die cast zinc. “Elastomers and plastic components can also be attacked. Carburetor and fuel gage floats are often made of plastic and have been known to swell and stick. Fiber gaskets can be softened and fuel hoses and pump diaphragms can swell or harden and crack.”

What this means is that the nature of motor gasoline should not be arbitrarily changed by government administrators without the most detailed consultation with the vehicle industry. Because motorcycles are greatly outnumbered by cars, it is possible that this consultative process may not include their manufacturers.

Why not just require all vehicles made after a certain date to be Flex-Fuel? First of all, any added system adds cost. An engine optimized for E85 would have a compression ratio too high for operation on ordinary gasoline, but with compression set at the high limit for gasoline fuel, when running on E85 we’d be throwing away some fuel economy which higher compression could have delivered. A vehicle returning a fuel mileage of 30-mpg on gasoline would deliver more like 22-mph on E85. The take-away here is that engines cannot be optimized across the range from common E10 to E85. A compromise is always present.

We have recently seen a proposal to build engines which could break this compromise – engines able to vary their compression ratio while operating. Certainly this is possible – the standard laboratory CFR knock-test engine has had this feature for seven decades – but it would add substantially to the cost, weight and complexity of engines.

The following label has been approved by EPA for placement on pumps capable of dispensing E15 fuel:


Like so many other things, the E15 controversy has acquired political aspects. Quoting from a USDA site; “Strong demand for ethanol production has resulted in higher corn prices and has provided incentives to increase corn acreage.”

Another USDA site gives figures for 2016 averaging just over 38% as the fraction of US corn now devoted to ethanol production.

You get the picture. Environmentalists are delighted at this use of corn because it satisfies their desire to see renewable energy sources replace fossil sources. The petroleum industry sees a gallon of fuel ethanol as 2/3 of a gallon of gasoline they don’t sell. A factory farming organization will naturally seek to increase the percentage of ethanol in motor gasoline. Think of being a Congressperson, deafened by the roar of all this lobbying. Is there any such thing as “right”? Or has right come to mean “what I want” while wrong means “what my opponents want”?

Still others see conversion of corn to ethanol as the institutionalizing of hunger in the form of “burning food.” Could it be, as claimed by some big-picture pundits, that the world-wide rise in food prices in part cause by conversion of corn to ethanol led to the social unrest and revolutions now referred-to as “Arab Spring”?

It’s giving me a headache. What do we do? We read and understand what it says on the pump before filling up. We write to our Congresspersons to let them know our concerns.

Happy motoring.




NOW BEAR IN MIND THAT I LIVE IN AUSTRALIA !!!  and from what I can figure out our fuels are a bit different from other parts of the world. BUT... there is a great deal of wrong information out there and even scary stuff that apparently might happen to you or your bike know premium unleaded re standard unleaded and how much they cost and how bikes run on them and all the rest......


Since I started riding airheads in the late 90's (yes I am a late arrival) with an R65 monoshock I have used either 95 or 98 RON fuels (and on advice at the time, FOR MY 70's BIKES, Valve Saver Flashlube at the prescribed rate). I did this as a result of discussions with people who had knowledge of fuels back then...people who worked in the fuel industry, someone who worked in the RAAF and had been to training sessions on the properties of unleaded fuels (as they were then) a result of all this I've run my airheads on premium fuels 95 or 98 RON since about 2,000 


It's been a long time since I updated my knowledge on this subject (although I've seen plenty of hearsay)  and so this morning I decided to go on a bit of a mission to discover what the state of hings are today. First I tried to read up on industry bulletins(very flowery and sweet smelling). then I looked into as many forums on the subject as I could find (scary) then I went to fuel company web sites looking for data sheets on the various fuels and information as to their uses and outcomes from same (more flowery and sweet smelling with no real commitment)...I might as well have gone on a UNICORN hunt.


In the end, I invested about 4 hours on the phone to Caltex, Shell and BP....In the end Caltex were the most helpful but it took a while. By staying on the line and passing through a number of hoops, I eventually got to talk to someone in service and tec support.  He was somewhere around my age and knew all about "older vehicles"

Of course he was not going to give up any company secrets or say anything  that could come back on the company but once I had explained about the bikes, the sort of carburetors they ran and what sort of seals and floats, O rings and diaphrams they used (yes he did know what a Stromberg CV was), we discussed compression ratios and so on. the distillation from my notes is this:


Unleaded fuels have changed dramatically since 2,000.

1: Although he didn't say this directly he said: Ethnol based fuels were not really suitable for our machines. He did say that they were much improved these days but .....

2: the octane rating of the fuel (correct terminology is RON but everyone refers to it as octane these days ) available to the general public is  91(standard) - 95 (premium) and 98 (super premium)

3: 91 (standard non ethanol) is basically just straight unleaded fuel as refined no additives other than base anti oxidants. He said that  most of the later unleaded type bikes (so post 1985) would run quite OK on this fuel but he agreed that because of the nature of the fuel there would be build up of soft gummy deposits over time.

4: 95 (premium non ethanol) higer octane base fuel more suitable for the older higher compression engines but hi opinion was that any of the bikes would benefit from using this fuel. Contrary to what I thought from my 2,000 induction to unleaded fuel, he thought that the higher octane would help some models and bikes but that the main difference was the "Vortex" additive pack in the fuel which was primarily a continuous cleaner. He pointed out that these additives were produced by Chevron / Texaco and had had such an amazing result since their introduction to Australian fuels "a little while ago" that they were now using the same additive in their diesel fuels. the upshot of all this was that in his view, with the types of main stream carburettors used on our bikes (so BING CV's) this was the best alternative.

5: 98 (super premium non ethanol) the highest octane ULP available in Australia. It has the same additive pack as 95 with a few extra tweaks (which in his opinion would make very little if any improvement on the fairly basic fuel system which exists on our bikes. When I explained to him that I had a 1974 model 750cc model that pings on anything but 98 regardless of any fix short of de - compression plates that I have ever tried. He said that of course, in an event like that the higher octane fuel COULD overcome that issue but that the only way to know was to run a few tanks through. He did say that he thought 98 was an expensive option if the bikes were running well on 95 or even 91 but he did day several times that he thought 95 was the correct fuel to use.

6: On the issue of the higher octane fuels or their additives damaging rubbers, diaphragms or O rings or floats, we had a long discussion about how long it might have been since carbs were rebuilt. Of course I couldn't speak for every one but I would have thought perhaps 6 to 8 years max. His considered opinion was that it would be very unlikely that O rings and floats etc purchased from reputable suppliers in the last 10 years would not be resistant to (a) unleaded fuels and (b) the additive packs in the premium versions .  He raised the point that any carb not rebuilt in the last 8 years would be very unlikely to be operating at its best in any case and that fuel additives or octane would be "down the list a bit" compared to gunk and air / vacuum leaks


So there you have it, improvements, changes and as much as I could find out "from the horses mouth" as it were. I urge you to use this blog to throw around some thoughts and to do your own research in your own country....don't just take the advice of someone who may not have updated his or her knowledge on the subject recently. As a result of my time yesterday and my experience with my own and others bikes, my recommendations to my customers will change as well.   






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