Ethanol fuel in vehicles

Ethanol has been mixed with petrol for many years. This is almost always bioethanol from renewable raw materials. One of the reasons why bioethanol is used is because it is almost completely CO2-neutral. In addition, significantly fewer harmful substances are released when ethanol is burnt than when burning petrol.

Another advantage is the higher octane rating of ethanol, i.e. its resistance to spontaneous self-ignition. This results in improved combustion and engine performance.

However, ethanol in fuel also has its downsides, as ethanol has a lower energy density than petrol. The higher the ethanol content in the fuel, the higher the consumption, which leads to a shorter range. However, this only comes into play at higher mixing ratios, as the additional fuel consumption is effectively approx. 30% for E85.

Although fuel consumption is increased due to the high ethanol content, pollutant emissions are lower than with conventional petrol with lower fuel consumption.

Another disadvantage is that ethanol leads to poorer cold-start properties. As a result, only special engines can run with a high ethanol content. 

Another aspect that has little to do with energy density, CO2 neutrality or pollutants is the origin of the bioethanol.

It is important whether the ethanol was obtained from waste or from potential food sources such as rape, maize or sugar cane. This creates a potential competition between food and fuel, but also between dependence and independence from fossil fuels.

Compared to conventional petrol-driven cars, flex fuel vehicles have some interesting adaptations, e.g. to the fuel system or the piston rings. The engines can be operated in any mixing ratio of petrol and ethanol (or methanol) or they can also be operated with pure ethanol. That’s where the term “flex fuel” comes from. In the case of Brazil, the proportion of vehicles with flex fuel engines is approx. 80%. 

Due to the poor cold-start properties of ethanol below 13°C, flex fuel engines have an additional fuel system with another petrol tank. By mixing in petrol, reliable vehicle starting can be guaranteed under all conditions. After the heating-up phase, the engine continues running with ethanol. 

Further development of the system does not require the additional fuel tank, but rather, heating elements bring the ethanol to the necessary temperature.

Overall, flex fuel vehicles are adapted to the operating conditions with ethanol so that there are no significant disadvantages compared to petrol operation.

Combined with independence from fuel type, potential price benefits and environmental protection, the stronger anti-knock properties and engine performance of ethanol offer good conditions for downsizing engines.

While E5 and E10 are widely used in Europe, E85 is more of a niche product. E85 can be used for refuelling in France and Scandinavia. In Germany, E85 was promoted for a while. After the end of the support, the E85 disappeared from the few petrol stations it was offered in.

Depending on the region and country, E10 is standard in North America, while E15 and E85 are continuing to expand there, with E85 only being suitable for flex fuel engines. Maize is commonly available in the USA in particular and is often used for the production of bioethanol.

Flex fuel engines are most widely available in Brazil, where E100 can also be used for refuelling. E100 consists of 93% ethanol and 7% water. In general, the ethanol content in fuel in South America is considerably higher, with E25 being standard in Brazil and E12 only having recently become available in Argentina.

 Africa is the exact opposite, as there is hardly any ethanol in fuel – with the exception of some countries and experiments.

In Asia, the picture is more nuanced, with production ranging from E10 to E20.

Australia and Oceania, on the other hand, are similar to European countries. 

Finally, it should be noted that the ethanol content in fuel continues to increase worldwide, resulting in dependence on fossil fuels being decreased and emissions reduced.