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E20 - petrol blended with 20 per cent anhydrous ethanol at a minimum Research Octane Number of 95 - became mandatory nationwide from 1 April 2026, notified on 17 February 2026.
Unblended petrol (E0) has been withdrawn from retail pumps, leaving no lower-blend option for older vehicles.
About 240 million of India's roughly 310 million petrol vehicles - close to 77 per cent, mostly two-wheelers - predate the April 2023 cut-off for E20-ready hardware.
India reached 20 per cent average ethanol blending by March 2025, five years ahead of its original 2030 target.
SIAM sent the government a communication on fuel contamination on 28 July 2026 and withdrew it in early August, saying the figures needed authentication, while reaffirming support for the programme.
Ethanol is an alcohol, not a hydrocarbon, and three of its properties drive the whole controversy. First, it carries roughly 30-35 per cent less energy per litre than petrol, so an identical tankful releases less energy and mileage falls unless the engine compensates. Second, it is hygroscopic - it pulls moisture out of the air. Past a saturation threshold of roughly 0.5 per cent water, the water-ethanol mixture separates out of the petrol and settles at the bottom of the tank, a phenomenon called phase separation, which corrodes steel tanks and can stall an engine. Third, it is a solvent that attacks certain elastomers: nitrile rubber (NBR) hoses, O-rings and pump diaphragms in older fuel circuits swell, harden and leak. Vehicles built after April 2023 use fluorinated rubber (FKM, commonly known by the trade name Viton) and powertrain control modules calibrated for ethanol, which is why the compatibility line falls where it does.
Simple Analogy: Ethanol in a fuel line behaves like a mild solvent in an old garden hose - it does not burst it on day one, but it softens and swells the rubber until a joint weeps. And because it drinks water from the air, a half-empty tank left standing slowly brews a watery layer at the bottom.
Ethanol blending in petrol stands at about 1.5 per cent; ethanol production about 38 crore litres
Blending rises through 8.17 per cent, 12.06 per cent and 14.6 per cent as grain- and sugarcane-based distillery capacity is scaled up
India reaches 20 per cent average ethanol blending, five years ahead of the original 2030 target
Notification issued mandating sale of petrol blended with up to 20 per cent ethanol at a minimum RON of 95
Mandatory nationwide E20 sale takes effect; unblended E0 petrol withdrawn from retail
SIAM sends the government a communication flagging chloride and moisture contamination and a rise in fuel-system component replacements
SIAM withdraws that communication, saying the figures require authentication through elaborate regional data collection and consultation with member manufacturers, and reaffirms support for the E20 programme
| Aspect | Vehicles built before April 2023 | Vehicles built after April 2023 |
|---|---|---|
| Design blend | Engineered for E5 or E10 | Engineered for E20 |
| Fuel-line elastomers | Nitrile rubber (NBR) hoses, O-rings, diaphragms | Fluorinated rubber (FKM / Viton) |
| Engine calibration | Powertrain control module not calibrated for ethanol | Ethanol-calibrated powertrain control module |
| Emissions benchmark | Earlier norms | BS VI Phase 2 with Real Driving Emissions norms |
| Share of the fleet | About 240 million vehicles, nearly 77 per cent | The remainder of about 310 million petrol vehicles |
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Petrol blended with 20 per cent anhydrous ethanol; E10 and E5 denote 10 and 5 per cent blends, and E0 is unblended petrol.
Ethanol with water almost entirely removed, the grade required for blending into petrol.
Able to absorb moisture from the surrounding air - the property that makes ethanol blends prone to phase separation.
The settling out of a water-ethanol layer at the bottom of a fuel tank once water content passes a threshold, causing corrosion and stalling.
A measure of a fuel's resistance to knocking; E20 has been mandated at a minimum RON of 95.
Society of Indian Automobile Manufacturers, the industry body for vehicle makers in India.