Bioethanol has lower energy content per liter than petrol. Manufacturers of FFVs usually inform customers that ethanol cars consume up to 30 to 40 per cent more fuel than conventional petrol cars. Theoretically it can be assumed that FFVs consume 1.41 times more E85 than unblended petrol on a volume basis.
Measures of real fuel-consumption
The evaluations carried out within BEST suggest that the energy efficiency when running on E85 is between 1 % to 26 % higher than when running on petrol. This results in a significantly lower E85 consumption than anticipated. In the best case only 1.14 times more E85 than petrol was necessary.
BEST carried out a detailed assessment of the technical performance of 93 FFVs across 11 different models. These vehicles were operated at all sites, sometimes by individuals and sometimes in car pools. In the periods that the cars were running on E85, the consumption on average was between 8.57 and 14.7 litres per 100 kilometres. When they were running on petrol they consumed an average of between 8.57 and 13.4 litres per 100 kilometres. The variations can in part be explained by different car models, different driving styles, the distance travelled and the type of journey (city traffic or motorway), fuel supply, etc.
Energy efficiency is an important area for future research. It is worth noting that E85 has a higher octane value than petrol. If engines could be adapted to this higher octane value in the future, increases in energy efficiency could be obtained and the fuel consumption of bioethanol cars could be reduced.