There is a lot of talk about E20, E85, and E100 fuels for vehicles in Bharat after Union Minister for Road Transport and Highways, Nitin Gadkari, recently announced that India has given legal recognition to 100% ethanol fuel to reduce dependency on imported fossil fuel and shift towards alternate clean energy sources to protect our environment.
Since 1 April 2026, E20 is the default petrol available to the public at pumps across Bharat. E20 is a blended fuel with 80% petrol and 20% ethanol. Though this shift has been a major focus of the government’s green energy initiative, the ongoing US-Iran conflict, leading to the closure of the Hormuz Strait, has hastened the process. For example, the E10, which is 10% ethanol blending milestone, was reached in 2022, and the transition from E10 to E20 (20% ethanol) happened in 2026, in just four years, much ahead of its original target of 2030.
There is an active public discussion about E20 fuel’s impact, and the conversation is mostly centered around three major issues: i) Mileage, ii) Wear and tear, and iii) Engine compatibility. The opinion is divided, while many accept E20 as a necessary transition from environment point of view, others feel that the rollout has moved too quickly, causing great concern for older vehicles compatible with E10 fuel. The question is whether the benefits outweigh the inconvenience caused to the owners of older vehicles. Let me elaborate on these concerns.
Mileage: Ethanol is produced from sugarcane and corn. It has emerged as the most prominent and technically feasible renewable fuel in the transportation sector. Because of its chemical structure, ethanol easily blends with petrol and burns cleaner, reducing carbon monoxide and hydrocarbon tailpipe emissions. However, there is a caveat: Ethanol contains ~33% less energy by volume in comparison to pure petrol, so blending it with petrol surely lowers the mileage. Let us find out how much?
The root of the issue is energy density. Pure petrol contains roughly 34.2 megajoules of energy per litre compared to roughly 21.1 megajoules per litre in ethanol. A megajoule (MJ) is a standard metric unit of energy, work, or heat. Since the energy density of ethanol is much less, blending it into petrol dilutes the total energy. So, an engine has to burn more blended fuel to produce the same power output, forcing the fuel economy to drop.
A rough theoretical calculation of the actual impact on mileage is provided here, with a caution that needs to be statistically proved by real test drives. A variation of ± 2 to 3 % could be possible. i) E10 – A 10% low energy ethanol blend with pure petrol reduces the fuel’s total energy content by about 3.3% to 4%. If your car is giving an average mileage of 15 km/litre on pure petrol, running it on E10 reduces its mileage by roughly 0.5 km/litre. and ii) E20 – A 20% blend will reduce the total energy by 7% to 8%. For that same 15 km/litre car, the drop from switching to E20 will be about 1.1 km/litre. But in the case of lightweight, highly fuel-efficient two-wheelers that give 60 km/litre mileage, an 8% efficiency loss due E20 fuel usage equates to a drop of ~4.8 km/litre. While the drop in mileage is a concern, the major worry is from the wear and tear as explained in the following.
Wear and Tear: Wear and tear will happen due to two factors. i) Moisture absorption ability of ethanol, and ii) Corrosive effects. Firstly, ethanol is highly hygroscopic, meaning it actively pulls moisture from the surrounding air. If a vehicle sits idle for extended periods of time, the accumulated moisture cause phase separation, which is a water-ethanol mixture that separates from the petrol and sinks to the bottom of the fuel tank, potentially causing engine misfires and severe internal rust.
Secondly, ethanol is highly corrosive in nature, stemming from its affinity to water. It readily absorbs and dissolves moisture from the air. When water mixes with ethanol, it promotes electrochemical corrosion and creates corrosive acidic byproducts like acetic acid that slowly degrade traditional rubber fuel lines, gaskets, and plastic seals, leading to fuel leaks and degraded engine components over a period of time.
Engine Compatibility: Most manufacturers in India began transitioning to engines and fuel systems designed for E20 fuel, coinciding with BS6 Phase 2 emission norms from 1 April 2023, as per the Government of India mandate. But not all BS6-compliant cars are automatically compatible with E20 fuel. Older BS6 Phase 1 models (pre-April 2023) are typically restricted to E10 fuel. Car manufacturers like Maruti Suzuki, Hyundai, Tata Motors, Mahindra, Toyota, MG, Kia, Skoda and Volkswagen began equipping their new petrol lineups with E20-resistant fuel lines, updated ECUs (Electric Control Units), and engine modifications as per the government mandate since April 2023.
As India aggressively pushes for flex-fuel vehicles (FFVs) to reduce crude oil imports, harmful carbon emissions and boost the agricultural economy, Maruti Suzuki has already launched its WagonR Bio-Flex model on 15 June 2026. This is India’s first mass-produced FFV passenger car, initially for commercial use, which can run on any blends from E20 to E85 (85% ethanol). Several other manufacturers like Toyota Innova Hycross, Toyota Corolla, Hyundai Creta, Tata Punch, Mahindra XUV 3XO, Maruti Brezza & Fronx have showcased their FFVs that are waiting to be launched next year. Others will follow.
In the two-wheeler segment, the Suzuki Gixxer SF 250 Flex Fuel motorcycle was launched in January 2025 and is available in select metros. Hero Splendor+ Flex Fuel and Hero HF Deluxe Flex Fuel have been officially launched this month and will be available to buyers from July 2026 onwards. The former is 250 cc, and the latter 100cc are the country’s first motorcycles designed to run on ethanol-blended fuel ranging from E20 up to E85.
A Catch-22 situation: The aggressive transition to E20 fuel in Bharat has sparked deep anxiety among owners of cars and two-wheelers purchased before 1 April 2023, despite their vehicles meeting BS6 standards. These vehicles were designed for E10 fuel and not for high ethanol blends. Making these old vehicles compatible to E20 will require modifications by manufacturers that will cost substantial money. A rough estimate for car upgradation to E20 points to an additional expenditure of Rs.50,000 to Rs.80,000 towards ECU recalibration, upgraded injectors, fuel lines, tanks, and engine tuning.
In my view, to make this transition fair and manageable, two issues need to be addressed by the government. Firstly, E10 petrol should be made available for older vehicles till consumers either opt for upgradation to E20 fuel compatibility or these are phased out. The decision should be left to consumers. A clear phase-out timeline needs to be issued by the government for the older vehicles, giving sufficient time to the owners to plan accordingly and avoid sudden financial pressure. Secondly, the price of E20 needs to be lower than the earlier E10 fuel because of its low energy density, which affects the mileage. To offset the disadvantage of lower mileage, the prices should be commensurately less with the increasing ethanol blend as the FFV market expands.
A report last week in India Today based on the on-road performance of the Suzuki Gixxer SF 250 Flex Fuel motorcycle suggests that the available E85 fuel priced at Rs. 82.12 should be reduced to Rs. 58 to achieve the same cost-per-kilometre parity with E20 fuel priced at Rs.102.12 in New Delhi. In other words, E85 would need to be around ~44% per cent cheaper than E20, rather than the current ~20% discount, to deliver mileage offset.
A few tips: Meanwhile a few tips are offered to the owners of the vehicles purchased before 1 April 2023 while using E20 fuel in their cars to avoid wear and tear. i) Use ethanol-compatible additives while filling E20 fuel, ii) Clean fuel injectors every 5,000–7,000 km as E20 can loosen old deposits leading to clog injectors, iii) Replace fuel filter every 5,000–7,000 km initially as E20 can loosen debris that can clog filters more often, iv) Inspect fuel hoses and seals every 10,000 km as ethanol can degrade old rubber hoses and O-rings and if required replace them with ethanol-resistant ones, v) Upgrade gaskets, seals, and O-rings to ethanol-safe materials.
- vi) Shorten oil change interval to every 5,000 km, vii) Check fuel pump regularly and watch for hard starting, whining noise, or power loss, viii) Clean fuel tank every 3 years to prevent moisture build-up and rust in the tank, ix) Allow engine to idle for 30–60 seconds before driving, x) Drain or use most fuel before longer inactivity. This will reduce ethanol exposure to moisture.
Final Verdict: The environmental considerations, national energy security, and economic diversification strategies have pushed India towards ethanol adoption. Bharat imports close to 90% of its crude oil requirements from various countries. Reducing dependence on fluctuating global crude oil supplies is a strategic priority till we discover new oil fields in our own territories or develop alternative technology-driven solutions. Automotive manufacturers, too, have a role to play by accelerating the adoption of materials proven to be ethanol corrosion resistant, such as stainless steel and fluoro-elastomers, throughout fuel system components as we move towards a higher ethanol blended fuel regime.
In my opinion, if this transition has to succeed, the most crucial factor would be to enforce stricter fuel quality standards with regard to contaminant limits in ethanol, such as water and chloride ion content that sneaks into the fuel primarily as a residue from the agricultural and industrial processes used to manufacture bioethanol. Any leniency on this issue will maximise the risk of accelerated corrosion and will lead to failure of this ethanol adoption policy.
Realising the fact that all energy sources are not perfect or ideal in every aspect, it is extremely important to strike a balance between economy and environment. If you think that the environment is less important than the economy, try holding your breath while you count your money.
