BENGALURU: As E20 petrol becomes the standard fuel across India, concerns continue to grow among owners of older cars and two-wheelers, particularly vehicles manufactured before 2023. Social media posts warning of engine failures and costly repairs have added to the confusion, but mechanical engineers from leading automotive companies who spoke to TNIE said the reality is far more nuanced.
According to the engineers, E20 fuel does not automatically damage engines. Instead, they said, higher ethanol content can expose weaknesses in ageing fuel systems, especially in vehicles that have not been maintained properly.
“E20 is different from the petrol many older vehicles were originally designed to use, but different does not mean destructive,” one engineer said. “The condition of the vehicle is often a bigger factor than the fuel itself.”
E20 is a blend of petrol containing up to 20 per cent ethanol. The government has promoted ethanol blending to reduce dependence on imported crude oil, improve energy security and support domestic biofuel production.
The engineers explained that ethanol has properties that make it behave differently from conventional petrol. It is a good solvent, meaning it can dissolve deposits that have built up inside fuel tanks and fuel lines over many years due to poor maintenance. While this cleaning action is not harmful by itself, the loosened deposits can travel through the fuel system and clog carburettor jets in older vehicles.
“This often creates the impression that E20 has caused the failure,” the engineer said. “In reality, the deposits were already present.”
Speaking on the mileage issue, one engineer said, “There will be a drop of around 5 to 6 per cent in mileage, as per Automotive Research Association of India (ARAI) tests. However, there are some cases of drop in mileage up to 10 per cent as well,” he said, adding that ethanol has lower calorific value than petrol, hence the car needs more fuel to run.
They also noted that ethanol is hygroscopic, meaning it can absorb moisture. In vehicles with damaged fuel caps or poor storage conditions, moisture can contribute to corrosion and contamination of the fuel system. The engineers said older carburettor-equipped vehicles are generally more sensitive to E20 than modern fuel-injected vehicles.
Carburettors rely on fixed mechanical settings and contain small passages, rubber seals and so on, that can be affected by age and accumulated deposits. In contrast, fuel-injected vehicles use electronic control units and oxygen sensors to adjust fuel delivery, allowing them to adapt more effectively to changes in fuel composition.
Even so, they cautioned that fuel-injected vehicles with ageing hoses, worn fuel pumps or clogged injectors could also experience problems if maintenance has been neglected.
The engineers recommended that owners of older vehicles inspect and replace cracked or hardened fuel hoses, ensure fuel tanks are free from rust, service carburettors where applicable and use fuel from reliable filling stations. They also advised against leaving vehicles unused for long periods with fuel sitting in the tank or carburettor, as storage-related issues can become more significant with ethanol-blended fuel.
They added that modern E20-compatible vehicles have been designed with ethanol-resistant materials and fuel-system calibration suited to the higher ethanol blend. Older vehicles, however, were developed at a time when lower ethanol blends were the norm, making preventive maintenance more important.
While acknowledging that some owners may experience fuel-system issues after switching to E20, the engineers said it is inaccurate to attribute every such problem solely to the fuel. They urged vehicle owners to rely on manufacturer guidance and proper maintenance rather than unverified claims circulating online. “The focus should be on understanding how the fuel behaves and keeping older vehicles in good condition,” one of them said. “Maintenance, not misinformation, is the key.”
