Classic Cars Used To Get Up To 18 Km/L, While Today's Cars Consume Much More

Classic Cars Used To Get Up To 18 Km/L, While Today’s Cars Consume Much More — Why?

Written by Romário Pereira de Carvalho

Published on 26/07/2025 at 10:56

Imagem: Reprodução

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In 1982, A Gol Running On Ethanol Surpassed 18 Km/L, But Environmental Changes And Flex Engines Made This Economy Hard To Repeat

Have you ever wondered why modern cars running on ethanol hardly exceed 18 km per liter? Even on highway trips, without using the electric system, this number seems out of reach. But 43 years ago, a popular model achieved just that.

In 1982, Volkswagen held the “VW Gol Alcohol Economy Tournament” in São Paulo. 520 taxi drivers participated.

The route was 37.2 km, with 85% on urban roads. The Gol fueled with ethanol recorded 18.32 km/l. An achievement that today seems impossible with current technology.

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In the 80s, the ethanol engines in cars were more efficient. Engineer Renato Romio, from the Mauá Institute, explains that these engines operated with a “lean mixture”.

This means: less fuel and more air at the time of combustion. The result was an energy efficiency of 85% compared to gasoline. Today, this number has dropped to 70%.

Ethanol burns faster because it contains oxygen. This helped to compensate for its lower calorific value. With the right adjustments, the engines of that time could extract the most from the fuel.

But everything started to change with the arrival of Proconve, a program created to control pollution caused by vehicles.

From the mid-80s, new regulations were adopted. And, in the early 90s, the catalytic converter emerged.

The catalytic converter requires a more controlled burn, with a balance between air and fuel. This meant that the mixture used in engines needed to be richer.

In other words, more ethanol to ensure the system works properly. The result was an increase in consumption.

Previously, ethanol consumed only 15% more than gasoline. Today, this difference is about 30%. The regulatory change had a direct impact on fuel economy.

Another important point is the emergence of flex engines. They were created to accept both ethanol and gasoline, or any mixture of the two. However, this versatility comes at a cost.

Ethanol performs better when used with high compression ratios. But gasoline doesn’t support the same conditions.

Therefore, flex engines adopt an intermediate ratio. This means that neither fuel can deliver the maximum possible performance.

Moreover, the gasoline sold in Brazil already contains 27% alcohol. This mixture directly affects engine performance, even when refueling with gasoline.

One alternative studied was the return to engines dedicated solely to ethanol. The former FCA (now Stellantis) even announced a 100% ethanol turbo model.

The idea was to recover some of the lost economy. But the project was canceled.

According to Romio, an exclusive ethanol engine could be more efficient than flex engines. It would not reach the 85% of the 80s, due to environmental requirements and the catalytic converter, but could reach 80%.

Even so, factors such as weather, off-seasons, and sugar prices make it difficult for ethanol to become the sole energy source for cars. For now, flex engines continue to be the standard in Brazil.

With information from Gazeta de São Paulo.

1 Comment

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Antonio Carlos Pereira

#152311

29/07/2025 20:25

Boa Noite na minha opinião o Etanol se não ouve-se tantas alterações seria o melhor combustível , fui prestador de serviço de uma Usina e a mesma forneciam o Etanol sem ser Alterado

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In 1982, A Gol Running On Ethanol Surpassed 18 Km/L, But Environmental Changes And Flex Engines Made This Economy Hard To Repeat

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In 1982, A Gol Running On Ethanol Surpassed 18 Km/L, But Environmental Changes And Flex Engines Made This Economy Hard To Repeat

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Four times faster than the Concorde, capable of taking passengers from New York to London in less than an hour at Mach 5.5, and with an engine that switches from turbojet to ramjet mid-flight at Mach 3.5, the Hermeus Quarterhorse went from paper to its first flight in just 19 months.

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