The concentration of ethanol used in petrol differs greatly from country to country. Hydrous ethanol which contains 4.5% water (alcool) has been used in all-ethanol vehicles in Brazil, but sales of these vehicles ceased in the 1990s to be replaced with a

blend containing 24% ethanol (Table 6.4). This change was probably introduced in order to avoid the modification of car engines to use 95.5% (E95) ethanol allowing the unmodified engines to use both petrol and the 24% blend. The modifications to run on E95 were a heated inlet manifold due to the cooling effect of ethanol, changes to the carburettor, the fuel tank and fuel line replaced by one in tin and cadmium brass. The fuel filter was changed to accommodate a higher fuel flow and the compres­sion increased to 12.1 because of the higher octane rating. Changes were also needed to the valve housings and catalytic converter.

In the USA, the initial blend contained 10% ethanol (Gasohol) but more recently a blend containing 85% ethanol (E85) has been introduced and flexible fuel engines have been developed which can use either E85 or petrol. Ethanol is also used in the USA to increase the oxygen levels in petrol with an addition of 7.6% and as a replace­ment for MTBE in reformulated petrol. Ethanol contains 35% oxygen which increases combustion and therefore reduces particulate and NOx emissions.