Biofuel is the mixture of gasoline and alcohol in different proportions, for use as a fuel in explosion engines designed to burn oil derivatives.
The proportion between both fuels is usually indicated by the percentage of ethanol preceded by a capital E. In this way, E10 gasohol is composed of 10% ethanol and 90% gasoline, and E85 is obtained by mixing 85% ethanol and 15% gasoline.
The E10 is a mixture of 10% ethanol and 90% gasoline that can be used in the engines of most modern cars without damaging them, although the exact effect on older engines is unknown. Mixtures E5 and E7 are similar, with 5 and 7% ethanol, respectively.
The proportions of ethanol in the mixture varies in each country, so in the USA the ratio commonly used is E10 and E15, in Brazil E20 and E25. In the USA, mixtures of up to E70 to E85 are used, especially in winter, to avoid starting problems with the engine cold.
The E95 contains 95% ethanol and has been used in buses with modified diesel engines that require 5% additive to improve ignition, since they use high compression to ignite the mixture, in contrast to the operation of gasoline engines in spark plugs are used.67 This fuel was developed in Sweden by the ethanol producing firm SEKAB. The trade name of this mixture is ED95.
E100 is pure ethanol, and is mainly used in Brazil. The alcohol or ethanol used as fuel in that country is the azeotrope and contains less than 5% water. However, since the nomenclature E is not adopted in the country, hydrated ethanol may be referred to as E100 to indicate that it does not contain gasoline.