E20 blended petrol helps reduce pollution by emitting less carbon into the atmosphere. The E20-compliant vehicles handle the fuel well and result in an efficient fuel system. However, a few older vehicle owners still need to be cautious due to the moisture-absorbing nature of ethanol.
TVS motor highlighted, "Because of its hygroscopic qualities, ethanol can draw moisture from the surrounding air. Phase separation brought on by this water absorption may result in corrosion if the manufacturer doesn't account for it."
Hero Motocorp wrote in Do's and Don'ts, "Since E20 fuel is hygroscopic in nature and attracts moisture from the atmosphere, consumers must take extreme care while washing vehicle / during the rainy season to avoid water entry in the fuel tank and ensure fuel cap is always properly and tightly closed."
It added that if a vehicle is required to be parked for a prolonged duration (more than a month), the fuel tank must be drained completely to avoid any damage to fuel pump / fuel tank and battery terminal must be disconnected before parking.
The Ministry of Information & Broadcasting, on August 4, 2026, released a video clarifying that that E20 fuel does absorb moisture and thus fuel systems, materials, corrosion resistance and storage protocols are tested by keeping the hygroscopic property in mind.
However, older vehicles are often less equipped to handle this due to ageing seals, hoses, and fuel-system components. Excess water contamination can lead to phase separation, where ethanol and water separate from petrol, increasing the risk of corrosion, rough running, starting difficulties, and reduced engine performance.
Notably, the Society of Indian Automobile Manufacturers in a 2022 release had said that the important deadlines decided for pan India implementation of E-20 are 2023 for vehicles to be material compliant, and 2025 for vehicles to be fully E-20 compliant.
How much moisture does ethanol absorb?
A study conducted by a leading trade association for America's ethanol industry - Renewable Fuels Association - showed that the moisture uptake rates of blends over three months of exposure for pure petrol was 0.4 parts per million (ppm) per day while that of E10 was 56.5 ppm/day, E15 64.8 ppm/day, E25 122.3 ppm/day and that of E83 was 166.8 ppm/day.
Higher the humidity, higher the moisture
Older vehicles across India do not tend to pose the same amount of risks. Vehicles in coastal areas with higher humidity are more vulnerable as there is more water vapour in the air surrounding the fuel tank.
For instance, Kota in Rajasthan has an annual relative humidity of around 44 per cent, as against 81 per cent humidity in Cherrapunji in Meghalaya and 79 per cent in Assam's Dibrugarh.
Meanwhile, there are a few brands that have been complying to the E20 norms ahead of time. Honda Cars India, in 2025, said that it embraced E20 petrol since 2009 and all Honda cars manufactured in India from 1 Jan 2009 have been E20 material compatible, demonstrating its unwavering commitment to its customers by providing them with the most advanced global products and services ahead of time. It added that the customers can freely use the E20 petrol in their existing Honda cars without durability concerns or need of changing any part in the car.
Also Read: Using E20 Petrol? These Parts In Older Vehicles May Need Replacement
