SAO PAULO, April 15 (Reuters) - The big four auto makers in Brazil joined forces with the Sugar Cane Industry Association (Unica) on Wednesday in a campaign aimed at expanding the use of cane-based ethanol in flex-fuel vehicles.

Local subsidiaries of U.S.-based General Motors Corp GM.N and Ford Motor Co (F.N: Quote, Profile, Research), Italy's Fiat SpA (FIA.MI: Quote, Profile, Research) and Germany's Volkswagen AG (VOWG.DE: Quote, Profile, Research) will together distribute 2 million free booklets explaining the benefits of ethanol for consumers who buy their flex-fuel cars in Brazil.

"Brazil's interest in ethanol is in accordance with GM's interest," said General Motors' CEO in Brazil, Jaime Ardila, in a news conference to launch the partnership.

The initiative is part of Unica's efforts to change consumers' view on the fuel.

Most flex-fuel car owners decide whether to use ethanol or gasoline based solely on which is selling at the cheapest price in the filling station. Unica believes that a bigger awareness of ethanol's environmental benefits would give demand a boost.

"This could help to improve ethanol consumption," said Unica's President Marcos Jank.

The material shows that ethanol has 90 percent less greenhouse gas emissions than gasoline -- partly because cane absorbs the carbon dioxide while it grows in the fields.

It also explains to consumers that they do not have to alternate the use of gasoline and ethanol in their cars for performance reasons, as some may think.

Together, General Motors, Ford, Fiat and Volkswagen account for 80 percent of the Brazilian auto market.