E20 petrol in pre-2022 cars: Engineer’s blog post against panic goes viral
Ashwin Durai, a Chennai-based mechanic, engineer and founder of ICD Tuning, argues that fears around E20 petrol are exaggerated.
- Jul 6, 2026,
- Updated Jul 6, 2026 6:45 PM IST
Even as social media is flooded with posts of vehicle owners venting out against the government’s E20 mandate, Ashwin Durai, a Chennai-based engineer, mechanic, and founder of ICD Tuning, has argued that much of this fear is exaggerated.
In a detailed blog post titled ‘E20 Petrol in Pre-2022 Cars – The Truth Nobody's Telling You’, Durai, who goes by Madras Mechanic, draws on years of workshop experience, race car tuning, and ethanol-based performance builds to explain why he believes most pre-2022 petrol cars, especially BS4-era vehicles, can safely run on E20.
Durai argues that viral claims of E20 "destroying" engines often confuse existing maintenance problems with problems caused by ethanol.
Most BS4 and newer petrol cars already have electronic fuel management systems capable of adjusting for E20, he claims, adding that modern fuel systems were designed with engineering tolerances that make a jump from E10 to E20 relatively minor.
Mileage drop still exists
The blog, however, acknowledges one downside: lower fuel economy. As ethanol contains less energy than pure petrol, drivers should expect a reduction in mileage. Durai argues that claims of 30–50% mileage reductions are inconsistent with the fuel's chemistry and with years of real-world usage.
To be clear, ethanol has 30% lower energy density than petrol. In August 2025, the Ministry of Petroleum and Natural Gas, citing studies by Indian Oil Corporation Ltd, Automotive Research Association of India and India’s apex auto industry body, the Society of Indian Automobile Manufacturers (SIAM), clarified that E20 causes a “marginal” 3–6% decrease in fuel efficiency in “older non-compliant” vehicles. The details of the study were never released.
Keeping the tank full
The blog post suggests vehicle owners keep the tank full to deal with hygroscopic nature of ethanol.
If a vehicle sits unused for extended periods in humid conditions with a partially filled tank, water absorption and phase separation can occur, the blog cautions.
However, he argues that this is primarily a concern for vehicles stored for weeks or months—not for cars driven regularly.
The blog concludes that owners of reasonably maintained BS4-era petrol cars should not panic about using E20.
At the same time, Durai advises owners of older BS3 and carburetted vehicles to take additional precautions, as these vehicles are more susceptible to ethanol-related issues.
For these vehicles, he recommends inspecting fuel hoses and seals, upgrading to ethanol-resistant components where necessary, tuning carburettors appropriately, and avoiding long-term storage with E20 fuel.
Even as social media is flooded with posts of vehicle owners venting out against the government’s E20 mandate, Ashwin Durai, a Chennai-based engineer, mechanic, and founder of ICD Tuning, has argued that much of this fear is exaggerated.
In a detailed blog post titled ‘E20 Petrol in Pre-2022 Cars – The Truth Nobody's Telling You’, Durai, who goes by Madras Mechanic, draws on years of workshop experience, race car tuning, and ethanol-based performance builds to explain why he believes most pre-2022 petrol cars, especially BS4-era vehicles, can safely run on E20.
Durai argues that viral claims of E20 "destroying" engines often confuse existing maintenance problems with problems caused by ethanol.
Most BS4 and newer petrol cars already have electronic fuel management systems capable of adjusting for E20, he claims, adding that modern fuel systems were designed with engineering tolerances that make a jump from E10 to E20 relatively minor.
Mileage drop still exists
The blog, however, acknowledges one downside: lower fuel economy. As ethanol contains less energy than pure petrol, drivers should expect a reduction in mileage. Durai argues that claims of 30–50% mileage reductions are inconsistent with the fuel's chemistry and with years of real-world usage.
To be clear, ethanol has 30% lower energy density than petrol. In August 2025, the Ministry of Petroleum and Natural Gas, citing studies by Indian Oil Corporation Ltd, Automotive Research Association of India and India’s apex auto industry body, the Society of Indian Automobile Manufacturers (SIAM), clarified that E20 causes a “marginal” 3–6% decrease in fuel efficiency in “older non-compliant” vehicles. The details of the study were never released.
Keeping the tank full
The blog post suggests vehicle owners keep the tank full to deal with hygroscopic nature of ethanol.
If a vehicle sits unused for extended periods in humid conditions with a partially filled tank, water absorption and phase separation can occur, the blog cautions.
However, he argues that this is primarily a concern for vehicles stored for weeks or months—not for cars driven regularly.
The blog concludes that owners of reasonably maintained BS4-era petrol cars should not panic about using E20.
At the same time, Durai advises owners of older BS3 and carburetted vehicles to take additional precautions, as these vehicles are more susceptible to ethanol-related issues.
For these vehicles, he recommends inspecting fuel hoses and seals, upgrading to ethanol-resistant components where necessary, tuning carburettors appropriately, and avoiding long-term storage with E20 fuel.