Imagine a country decides, over a few short years, to change what it pours into its cars. Not a pilot scheme in one city, not a niche for early adopters, but a large-scale shift in the passenger-car fuel system.

Brazil did exactly that in the space of a decade. Then the ethanol-only car boom fell apart, and the way it fell apart is the interesting part. The engineering worked. The new-car market switched over in a few years. The thing that broke the model wasn’t the technology. It was that the system depended on oil and sugar prices, reliable ethanol supply, and continuing government support.

The oil shock that made Brazil rethink the whole fuel supply

The trigger was the 1973 oil crisis.

When world crude prices jumped, Brazil was badly exposed: in 1973 its oil deficit was 77.3 percent, or about 586,000 barrels of oil equivalent per day, reflecting its heavy dependence on imported oil.

Rather than simply eat the cost, Brazil went looking for something it already had a lot of: sugarcane. Cane can be fermented and distilled into ethanol, and ethanol can move a car.

Brazil set up its National Alcohol Program, Proálcool, on November 14, 1975, to expand ethanol production and substitute it for part of the gasoline used by light vehicles. The first phase focused on blending ethanol into gasoline; after the second oil shock, the program shifted toward cars that could run directly on hydrous ethanol. 

How Proálcool turned sugarcane into a national fuel program

This was not a light-touch policy. The program used subsidies, financing, state involvement in purchasing and distribution, blending rules, and tax incentives, aimed at building the whole chain at once: more cane, more distilleries, fuel pumps, and cars that could burn ethanol.

The first car that ran on ethanol alone, not merely a gasoline blend, became commercially available in 1979.

Production of the fuel moved just as fast. Brazilian ethanol output climbed from 0.6 billion liters in 1975 to more than 12.7 billion liters by 1992. Whatever you think of the economics, Brazil built the physical capacity to fuel millions of cars on a crop, and it did it fast.

The exact share varies by year and source, but the switch to ethanol-fueled cars was steep. Jennifer Eaglin, drawing on industry data, writes that “By 1985, over 95 percent of all new cars on the road ran exclusively on ethanol.”  

Why it fell apart 

For buyers, a car that burns only ethanol is attractive if the fuel is competitively priced and reliably available. However, both conditions came under pressure at the end of the decade.

A nationwide ethanol shortage hit in 1989 as government support weakened. A 2016 paper on the history of Proálcool lists the pile-up: falling oil prices, low domestic ethanol prices, high international sugar prices, and limited government resources all helped undermine the ethanol-only market. With sugar fetching more abroad, mills had an incentive to turn cane into sugar rather than fuel.

The boom in pure-ethanol cars had run its course.

The flex-fuel comeback 

Ethanol didn’t disappear from Brazil so much as change shape. The comeback came through flex-fuel engines, which can burn gasoline, ethanol, or any mix of the two. Volkswagen launched the Gol Total Flex in 2003, and flex-fuel cars rapidly came to dominate new-car sales, exceeding 90% of new cars in 2013. 

The 1980s version was a bet exposed to commodity prices and government policy. When oil got cheap, sugar got dear, subsidies weakened and ethanol ran short, a driver with a pure-ethanol car had no alternative.

The flex-fuel car didn’t make ethanol permanently cheaper or guarantee supply. It moved the choice from the factory to the filling station. Instead of committing years in advance to one fuel, the driver chooses at the pump.

Brazil’s first attempt asked people to trust the ethanol supply before buying the car. The second lets them keep their options open until the moment they fill up. The engineering was never really the weak point. Flexibility was.