Ethanol-blended petrol push: Car experts warn E20 petrol may reduce fuel efficiency by 2 to 5 percent; warn of long-term erosion impact

The adoption of 20 per cent ethanol-blended petrol (E20) could lead to a 2-5 per cent reduction in fuel efficiency, depending on the type of vehicle, according to automotive industry experts.India is fast-tracking its shift to E20 fuel, a mix of 20% ethanol and 80% petrol, aimed at lowering carbon emissions and reducing reliance on imported crude oil. The nationwide rollout, initially scheduled for 2030, has been moved up to 2025.Engineers associated with major automakers said older vehicles that are not E20-compliant may experience long-term wear in components such as gaskets, fuel hoses, and pipes, though these issues are not expected to appear immediately.”There can be a drop in mileage ranging from 2-5 per cent, depending on the type of vehicle. This is purely because of the lower calorific value of ethanol compared to petrol,” an expert, who requested anonymity, was quoted as saying by PTI.Earlier this month, the Oil Ministry clarified that claims suggesting E20 causes a “drastic” reduction in fuel efficiency are misplaced. The ministry noted that E10 vehicles have shown only marginal efficiency drops, saying, “for some manufacturers, vehicles have been E20 compatible from as far back as 2009. The question of any drop in fuel efficiency in such vehicles does not arise.”The ministry highlighted that vehicles tuned for E20 deliver better acceleration, a key factor in city driving, and that ethanol’s higher heat of vaporisation reduces intake manifold temperatures, increasing air-fuel mixture density and boosting volumetric efficiency.”Ethanol, being lower in energy density than petrol, results in a marginal decrease in mileage, estimated at 1-2 per cent for four-wheelers designed for E10 and calibrated for E20, and around 3-6 per cent in others,” the ministry said through a post on X earlier this month.Several reports indicate that many motorists are concerned about E20 fuel’s potential impact on fuel efficiency.A Public Interest Litigation (PIL) was filed in the Supreme Court last week, challenging the nationwide rollout of 20% ethanol-blended petrol (E20). The plea, submitted by advocate Akshay, contends that millions of vehicles, including cars and two-wheelers made before 2023 and some newer BS-VI models, are not designed to run on high ethanol blends.

How leading automakers reacted

When approached for comments, Maruti Suzuki and Hyundai Motor India declined, while a Tata Motors spokesperson confirmed that their vehicles are E20-compliant.”E20 usage will not have any impact on engines of compliant vehicles, as the materials are tuned for it. However, in vehicles, which are not E20 compatible, there could be erosion of gaskets and fuel rubber hoses and pipes in the long term, but not immediately,” another spokesperson was quoted as saying by PTI.The government has been promoting E20 blending as part of a national programme aimed at reducing emissions and boosting farmers’ income through ethanol production from sugarcane and maize.



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