Ethanol Fuels E100 E85

24 October 2018

Ethanol is being used as part of the blend for the “biofuels” that are increasingly popular as governments put lower pollution targets in place. Ethanol is renewable and produces far lower emissions than gasoline alone. It’s usually found in dual-fuel or flexible fuel cars, but its wider take-up has been hampered until now by a lack of infrastructure – that is, pumps at filling stations in convenient locations for motorists.

When ethanol is added to fuel, the resulting blend is characterised by a label that begins with an “E”. Ethanol fuels E100 E85 are two of the more common ones. The number following the “E” denotes how large a percentage of ethanol is present in the mixture. So E85 is composed of ethanol at 65 to 85% and gasoline at 15 to 35%. E100 is thought to be pure ethanol but can contain up to 5% water and other contaminants coming from the ethanol production such as acids

E85 – Uses Worldwide

E85 is frequently used in Europe and the US for flexible-fuel vehicles. In general, this is the fuel with the highest percentage of ethanol available in these countries. Normal gasoline has an AKI octane range of 87-93, while E85 is rated at 94-97. (AKI = RON + MON / 2)

However, during very cold weather, fuels containing a high percentage of ethanol may not provide reliable fuel ignition in vehicles. So some lower ethanol blends, such as E75, may be provided at filling stations during winter periods. The blend is labelled at the pump as E85 and is intended for flexible fuel vehicles.

Uses for E100

E100 is almost 100% ethanol. Brazil has led the way in the use of hydrous ethanol, as this fuel is called, partly as a result of the energy crises in the 1970s, when alternatives to gasoline were sought. But recently, flexible-fuel vehicles have been increasingly widely used.

In fact, the Brazilian fuel isn’t quite 100% pure ethanol. The “hydrous” description gives away the fact that it contains 3.5% water by volume. However, this is the highest possible concentration of ethanol that can be produced by a simple distillation process. And since the water isn’t an additive but simply a by-product of the production distillation, the mixture can be described as 100% ethanol.

Once again there are cold-start problems with this fuel if the temperature is below 15 C. So most of the E100 flexible fuel vehicles have a small reservoir of gasoline to help start the engine when it is cold. As soon as the engine starts, the vehicle switches to using ethanol. However, newer ethanol cars have got round the problem by warming the ethanol before it is used to start the engine.

Need for New Additives and Fuel Blends

Ethanol may be kind to the environment, but it’s less kind to engines that haven’t been designed to cope with it. It’s corrosive, so engines need to be modified if they have been designed purely for gasoline. Obviously, the search is on for additives that will preserve ethanol fuels E100 E85 low emissions while improving their cold-start performance and protecting gasoline engines from their effects.

Coryton is able to produce all grades of Ethanol containing fuels including different contaminants which are typically found in Ethanol containing fuels for test purposes.


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