ETHANOL and its Effects on Motorcycles.

Recent debates and publicity concerns surrounding the introduction and use of ethanol has raised the question of its effects on the materials used in our vehicles.

The use of ethyl alcohol mixed with petrol up to concentration of 10% (E10) has been common practise since the fuel crisis of the 1970's. This blend is now regularly available in Australia and in limited supply throughout Europe. Higher levels of mixes of 22% to 85% (E22 to E85) are used in Brazil and the latest trend has been for vehicle manufacturers to develop Flexible Fuel Vehicles (FFV's).

These FFV's and South American vehicles have all been specifically designed to accommodate the use of these high concentrations of ethanol.

Advantages and Disadvantages

The addition of ethanol to petrol has an effect on both the performance of an engine and also its interaction with the different materials it comes into contact with.

Change in Octane Number

The addition of ethanol, up to a certain level, improves the octane number giving better anti-knock properties that can be helpful to older and higher performance engines that were designed for high octane fuels.

Change in Volatility

A fuel's ability to vaporise has an effect on performance and on emissions. The addition of ethanol has the effect of lowering the temperature at which the fuel vaporises thereby improving combustion and cold starting but can increase the possibility of a vapour lock.

 Increase in Oxygen Content

In addition to hydrogen and carbon ethanol also contains oxygen. The replacement of hydrocarbons with oxygen has the effect of weakening the air-to-fuel ratio. This lowers emissions, lowers mpg and raises NOx in vehicles without a three way catalyst.

Effect of Water Solubility

The addition of ethanol causes fuel to become hygroscopic (absorbs water). This has several different effects. It becomes acidic and conductive causing both a chemical reaction with certain materials and galvanic reaction causing corrosion. As water is heavier than petrol then a layering effect can occur with stored fuel having a higher water content settling to the bottom where fuel pick-ups are located.

Lubricating Effect

When mixing with 2 stroke fuels it has been noted this can cause phase separation in breaking down the oil and petrol content causing a loss of lubrication. Under other conditions it can act as a solvent washing oils from metal surfaces thereby increasing engine wear.


Ethanol readily permeates through elastomers and plastics resulting in a deterioration of these materials.


The AMAL Company has already made changes of materials in sensitive components. Needles are produced in nickel silver whilst orifices are made from manganese bronze. Diaphragms and O rings have been upgraded to Viton or other suitable material.

Reprinted from the AMAL Company's technical library.

A little “Tip” I picked up from another web site that might be of interest to some of the club members.

Some think octane is a chemical additive in gasoline. Octane is a number that standardizes the performance of gasoline. The higher the octane number the slower the fuel burns. If fuel burns too quickly, it reaches super sonic speed. The pinging you hear is the burning fuel breaking the sound barrier. The crack of a bull whip is the same thing, as it exceeds the speed of sound.

In WWl it was discovered that tetraethyl Lead was a big enhancer of the performance of gasoline. Back in the day (1946), filling stations offered two grades of gas, 79 octane regular, and 85 octane ethyl. Detroit was getting with the program around 1954 as far as raising compression ratios, many having 10 to 1. The gas octane was raised to meet the need, to 86 octane regular, and high test or ethyl, 94 octane.

A company called SUNOCO, in 1956, had a 'dial a grade' pump at all of their filling stations. You were able to purchase gas with over 100 octane. They started with 5 different blends, then later changed to 8 different blends, increasing octane respectively.

In 1958, to be competitive, all filling stations were offering at the pump three grades, 90, 98, 100. About this time, nickel was being used as well to enhance fuel performance.

Phil Dansby

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Revised: January 05, 2018.