Higher ethanol boosts race car acceleration, but does it help our mass-market vehicles?

Can higher ethanol blends really make your car or bike faster? While racing engines benefit from ethanol's unique properties, does E20 or E85 deliver any real performance gains in our everyday vehicles? Let's find out.

Union Petroleum and Natural Gas Minister Hardeep Singh Puri recently reignited the debate around ethanol-blended fuels by arguing that ethanol is not only a cleaner alternative to petrol but can also enhance vehicle performance.

Responding to concerns over reduced fuel economy under India's ethanol-blending programme, Puri cited motorsport as an example. "Somebody is saying that fuel mileage is going to drop. It is now well established that ethanol is even used in racing cars. Acceleration improves. Knocking also improves. Mileage? Yes, it may drop a little. But it may drop slightly due to various factors," Puri said. His remarks raise an obvious question. If ethanol contains less energy than petrol, how can it improve acceleration? And more importantly for Indian motorists, does moving from conventional petrol to E20 or even E85 in flex-fuel vehicles actually make a noticeable difference in everyday driving?

Why racing cars become quicker on high-ethanol fuel

On paper, ethanol appears to have a disadvantage. It contains less energy per litre than petrol. Pure ethanol (E100) has roughly 30 per cent lower energy density than petrol, which is why higher ethanol blends generally reduce fuel economy. However, outright performance depends on much more than just the energy content of the fuel.

Speaking to Auto Today, Vikram Gulati explained that ethanol's biggest advantage lies in its combustion properties. "Formula One cars, which represent the best of performance, use ethanol, so you get much better torque and much better acceleration using ethanol than with petrol." Ethanol has a higher octane rating than petrol and is much more resistant to knocking or pre-ignition. This allows engineers to build engines with higher compression ratios, more aggressive ignition timing, increased turbo boost and fuel maps specifically optimised for ethanol.

These changes enable the engine to generate more cylinder pressure and extract more power despite ethanol's lower energy content. That is why racing cars can produce better acceleration and higher performance using ethanol-rich fuels. As Gulati noted, however, ethanol's lower energy density remains a scientific reality.

"The issue really is the lower energy density of ethanol versus petrol. Therefore, your mileage does drop, but there is science behind it. If you look at the chemical formula of the two products and the energy content, you can easily figure out that the difference is going to be around 30 per cent if you're using E100. Some of that can be recovered by engineering the engine to some extent."

In short, ethanol delivers better performance only when the engine is purpose-built to exploit its characteristics.

What about E20, the fuel most Indians use today?

This is the question that matters to the average car or motorcycle owner. India has now widely adopted E20 petrol, which contains up to 20 per cent ethanol. Compared with pure petrol (E0), E20 does have slightly lower energy density. However, the difference is relatively small because only one-fifth of the fuel consists of ethanol. In modern mass-market vehicles that are E20-compatible, manufacturers calibrate the engine management system to ensure that power delivery, drivability and emissions remain virtually unchanged on E20. The engine control unit continuously adjusts ignition timing, fuel injection and air-fuel ratios to compensate for the change in fuel properties.

As a result, most drivers are unlikely to notice any meaningful difference in acceleration, throttle response or top speed when switching between E0 and E20. The biggest difference is usually seen in fuel economy, which may decline slightly because of ethanol's lower energy content. For most E20-compatible vehicles, the reduction is generally limited to a few percentage points rather than a dramatic drop.

Does E85 make flex-fuel vehicles quicker?

The answer is also largely no.

Flex-fuel vehicles sold in India, such as the Maruti Suzuki WagonR Flex Fuel, are designed to run on anything from petrol to E85. Their engines automatically detect the ethanol content and adjust fuel delivery and ignition accordingly. However, unlike racing engines, these powertrains are not designed exclusively around E85. Manufacturers deliberately prioritise reliability, emissions compliance, durability and seamless operation across multiple fuel blends instead of maximising power on high-ethanol fuel. They do not substantially increase compression ratios or adopt aggressive engine tuning because the same engine must continue to perform reliably on petrol, E20 and E85.

Consequently, while E85 retains ethanol's superior anti-knock characteristics, most of its theoretical performance advantage remains unused. Drivers should therefore not expect a noticeable improvement in acceleration simply by filling E85 instead of E20.

Our real-world test supports this

To understand how E85 performs outside laboratory conditions, we recently tested the Suzuki Gixxer SF 250 Flex Fuel, one of India's first production motorcycles capable of running on fuel containing up to 85 per cent ethanol.

The motorcycle was first filled with E20 and ridden for 124.2km. It was then refuelled with E85 and ridden over an almost identical 127km route under similar conditions.

The outcome was revealing. There was virtually no noticeable difference in acceleration, throttle response, engine refinement or overall performance between the two fuels. Even the exhaust note remained largely unchanged.

Fuel efficiency, however, changed dramatically

With E20, the motorcycle covered 124.2km while consuming 2.44 litres of fuel, returning 50.9kmpl. On E85, it travelled 127km but consumed 4.37 litres, resulting in an efficiency of just 29.06kmpl. That translates to a fuel efficiency drop of nearly 43 per cent, despite delivering almost identical real-world performance.

The claim that ethanol improves performance is technically correct but only under specific conditions. In racing engines that are purpose-built for high-ethanol fuels, ethanol's high octane rating allows engineers to increase compression ratios, optimise ignition timing and extract substantially more performance. That principle, however, does not directly translate to road-going vehicles.

For the vast majority of Indian motorists using E20 petrol, switching from pure petrol (E0) to E20 is unlikely to produce any noticeable change in acceleration or performance. Modern E20-compatible engines are calibrated to maintain virtually identical drivability, with only a small reduction in fuel economy due to ethanol's lower energy content.

The same holds true for flex-fuel vehicles running on E85. While they can safely operate on much higher ethanol concentrations, their engines are tuned for flexibility rather than outright performance. As our Suzuki Gixxer SF 250 Flex Fuel test demonstrated, E85 offered virtually no perceptible gain in acceleration but resulted in a significant reduction in fuel efficiency.

For consumers, the biggest consideration therefore remains economics rather than performance. Unless higher ethanol blends such as E85 are priced substantially lower than E20 or petrol, their reduction in fuel economy is likely to outweigh any negligible gains experienced in everyday driving.

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