E20 petrol debate: Kerala motorists cite mileage drop, fuel system issues as experts seek transparency

Kochi: For nearly three decades, Kochi-based vintage motorcycle enthusiast Sam George never had to question the reliability of his 1995 Yezdi Road King. It consistently delivered around 35 kilometres per litre and, apart from routine maintenance, rarely required major repairs. That changed, he claims, after petrol pumps switched almost entirely to E20, the petrol blended with 20% ethanol.

“The mileage suddenly dropped to nearly 25 kmpl. Initially, I thought the carburettor’s fuel jet was clogged, so I cleaned it. But the problem kept returning,” George told Onmanorama.

Eventually, he had to replace the carburettor after its rubber components deteriorated. Finding a replacement for a motorcycle over three decades old was difficult, and it cost him about ₹3,000. Soon afterwards, his 1990s Jawa developed similar issues. More surprisingly, George says even his recently purchased BS6-compliant 400cc motorcycle developed a clogged fuel cap that eventually had to be replaced.

“The government says riding style can affect mileage. But I’ve been riding this Road King for nearly 30 years. My riding style didn’t suddenly change when E20 arrived. I know this motorcycle inside out, and the drop started only after E20 became the standard fuel,” he says.

George’s experience is one of many complaints now emerging from Kerala. While there is no conclusive scientific evidence establishing that E20 alone causes engine failures, mechanics, motorists and road safety experts say they are increasingly hearing reports of reduced fuel efficiency, deteriorating rubber components and moisture-related fuel system issues, particularly in older vehicles. They are now calling for greater transparency and long-term independent studies on how the fuel affects India's vast fleet of vehicles.

Across Kerala, E20 has become the default petrol available at fuel stations. Unlike earlier transitions to cleaner emission norms, motorists had little choice in the matter. Owners of decades-old motorcycles now fill up with the same fuel used by brand-new ‘E20-compatible vehicles’, raising questions over how older engines will perform over time.

E20 and concerns
E20 is a blend of 80% petrol and 20% ethanol, a biofuel produced primarily from sugarcane, maize and surplus food grains. The Centre accelerated its nationwide rollout as part of its strategy to reduce dependence on imported crude oil, lower emissions and improve farmers' incomes.

Summaries released by NITI Aayog indicate that prolonged exposure to E20 can accelerate deterioration of certain rubber hoses, seals and gaskets because ethanol is both corrosive and hygroscopic; it readily absorbs moisture.

The Ministry of Petroleum and Natural Gas challenged critics to produce a single verified case where an engine suffered catastrophic failure solely because of E20 fuel.

Vehicle manufacturers like Maruti Suzuki have said it extensively tested E10-designed vehicles on E20 fuel and found no significant concerns. The government has clarified that using specification-compliant E20 petrol does not invalidate vehicle warranties or motor insurance policies, a position endorsed by the Society of Indian Automobile Manufacturers (SIAM) and insurers, including ICICI Lombard.

What Kerala mechanics say
Although manufacturers insist there is no evidence of widespread damage, automobile mechanics say customer complaints have noticeably increased.

“We don't see engines failing overnight because of E20,” says Subhash, a senior service advisor at a leading automobile service centre in Kochi. “But customers consistently complain about reduced mileage. For older vehicles, running on very low fuel levels makes the situation worse because moisture and ethanol tend to accumulate at the bottom of the tank.”

The drop in fuel efficiency is not entirely unexpected. Ethanol contains less energy than petrol, meaning engines generally need to burn slightly more fuel to travel the same distance. For commuters, even a small reduction matters.

“I ride my 110cc scooter around 30 kilometres every day for work,” says Siddharth Nair, a Kochi-based corporate executive. “I used to get around 50 kmpl. Now I'm getting barely 44 kmpl. That means spending noticeably more on fuel every month. Many people say it is because of the E20 fuel but the government denies it. We don’t know the truth.”

Petrol pump employees say they are often caught between frustrated motorists and a policy they have no control over. “Customers regularly complain that our petrol quality has become poor because their tanks are emptying faster. We have to explain that this is the standard fuel being supplied,” says an attendant at a fuel station in Vytilla.

Separating anecdotes from scientific proof
Experts caution against drawing direct conclusions without comprehensive research. “Scientifically proving that a particular engine failed solely because of E20 is extremely difficult,” says Dileep Kumar G, former Motor Vehicles Department inspector and now Deputy Director of the SCMS Institute of Road Safety and Transportation, Ernakulam.

“That would require controlled testing of identical vehicles over long periods. An ordinary consumer cannot measure combustion characteristics or chemical changes inside an engine. But the increased volume of complaints reaching workshops today cannot simply be ignored.”

According to Sam George, vehicles that remain unused for long periods are especially vulnerable.

“When E20 sits inside a fuel tank for weeks, it absorbs moisture. That moisture eventually causes rust and damages rubber components inside carburettors. Older bikes allow you to shut off fuel and run the carburettor dry. Early fuel-injected motorcycles don’t offer that option. If the injection system is damaged, repairs can easily cost ₹20,000 to ₹30,000,” he says.

Mechanics also report seeing premature hardening of fuel lines and deterioration of rubber seals in some older petrol vehicles, although independent long-term studies establishing a direct causal relationship remain unavailable.

“Customers report poor mileage and we cannot give them a satisfactory response. Even my own car, a 2021 model, saw around a 4-litre drop in mileage after using E20 fuel. But proving it needs better studies,” said Sumith S, a service advisor at an automobile outlet in Kottayam.

Calls for greater transparency
For road safety and automobile experts, the debate is no longer just about ethanol; it is about transparency. “What concerns me is that millions of Indians buy vehicles expecting them to remain reliable for 15 to 20 years,” says Upendra Narayanan, Director of the Indian Institute of Road Safety and a nominated road safety expert for the Kerala Road Safety Authority and Council.

“We spent years improving engines to meet stricter emission norms. Introducing a significantly higher ethanol blend across the country requires equally robust public research.”

Narayanan says detailed performance data should be made available, including long-term studies on fuel system durability and possible effects on emission testing under the existing Pollution Under Control (PUC) framework.

Until more long-term data becomes available, mechanics advise owners of older vehicles to avoid running tanks nearly empty, keep fuel systems clean, inspect rubber hoses and gaskets regularly, and, where possible, drain carburettors before storing vehicles for extended periods in an idle position.