'Reduced mileage, engine damage, frequent service visits': Why people are wary of E20 petrol despite Centre's assurance

Despite the Centre’s assurance that the mileage drop from E20 fuel isn’t ‘drastic’ and that older vehicles will not suffer damage, many Bengalureans remain wary. E20 is a fuel blend comprising 80% petrol (gasoline) and 20% ethanol (a biofuel).

Social media users have recently reported reduced mileage, engine damage, and more frequent service visits after switching to E20. This chatter follows union petroleum minister Hardeep Singh Puri’s announcement that India has achieved 20% ethanol blending, five years ahead of its 2030 target. In response to the backlash, the ministry posted online that proper engine tuning can mitigate mileage drops — estimated at 1-2% in E10 vehicles calibrated for E20, and 3-6% in older models. In vehicles that have run for more than 20,000 km, rubber gaskets may need replacement. It is a low-cost fix, the post said.

Several people Metrolife spoke to reported a 1-2 km drop in mileage, a 10% reduction in tank range, and even “jerks while driving”. During servicing, mechanics could not pinpoint what was causing the problem. The only variable, they suspected, was the fuel. Oil marketing companies began selling E20 in 2023, but users say they noticed these changes only this year.

Pearl Win, a former automobile journalist, owns two bikes. One is custom-built and ethanol-compliant, the other is optimised for conventional petrol. “On the compliant bike, mileage jumps from the usual 180-200 km/l to 260-280 km/l when I use the blended petrol. Throttle response is also great. But when I use ethanol-blended petrol (EBP) on the regular bike, I have noticed a power drop after riding about 5 km,” he says.

Vintage bike owners are especially concerned. Vishal Agarwal, founder of the Bangalore RD350 Club, says two-stroke engine bikes require oil mixed with conventional petrol. Ethanol blending, to him, feels like “dilution”. “We don’t know how these bikes will behave. And if there’s damage, spare parts are hard to find,” he says. Gokul M, a publicist who restores vehicles, shares the concern. “My regular bike runs fine, but the fear (concerning vintage vehicles) is real. These machines have sentimental value—some are handed down from fathers. Parts are hard to find, and we can’t afford damage.”

Pratima S, a marketing and communications professional, has delayed her car purchase due to concerns over E20. “A car is a big investment. I don’t want to risk its longevity,” she says. She also wonders if warranties will cover ethanol-related damage.

Though EBP and regular petrol are priced the same, users say they should have the option to choose between them. Many are unsure what fuel they are filling their vehicles with, as fuel stations often lack clear labelling. 

In light of the recent concerns, sales professional Ramanand K P has switched to a brand that sells petrol with 17% ethanol. Raghav Kini, a chief revenue officer, is considering a premium petrol-only fuel that is costlier than the usual petrol.

'Established technology'

Experts like Santhosh K, professor of mechanical and industrial engineering at the Manipal Institute of Technology, explain that fuel efficiency drops because ethanol has lower energy content (21.1 MJ per litre versus petrol’s 34.2 MJ). For E10 users, this could mean spending an additional Rs 290 per month on fuel, he estimates.

Even in the case of ethanol-blended diesel, researchers like Deepak B have noticed fuel inefficiency. He is a PhD scholar researching on ‘Micro-emulsion Biofuels’. “I have seen a 2.7% reduction in terms of thermal efficiency, which in turn affects mileage,” he says.

Santhosh goes on to add that despite being produced domestically, ethanol-blended petrol isn’t cheaper than regular fuel due to the high cost of specialised infrastructure and handling, unchanged taxes, and pricing tied to global crude rates. Supply also fluctuates with monsoon-dependent crops like sugarcane. The aim of blending, he notes, is not to lower prices but to reduce emissions, enhance energy security, and support rural incomes.

Prof R V Ravikrishna, an internal combustion expert at IISc Bengaluru, calls EBP a “well-established technology,” citing the example of Brazil, where pure petrol is no longer sold. “In Brazil, people can choose how much petrol and ethanol they want blended at fuel stations,” he notes. In his lab tests, conducted on a small engine three years ago, ethanol blends performed on par with petrol; even at higher ethanol percentages.

Dayananda G N, project consultant at the Karnataka State Bioenergy Development Board, says they have never received complaints concerning EBP — from its calorific value to moisture content. He cites a 2014 pilot in which Nagpur’s municipal buses reportedly ran on 100% ethanol.

Public scepticism is common with emerging technologies, says Prof T V Ramachandra, also from IISc. His team’s combustion tests in 2021-22 also found no issues with ethanol.

Nandakumar M B, professor and head of the automobile engineering department at Dayananda Sagar College of Engineering, acknowledges cold-start issues that can arise with EBP in older vehicles. “Ethanol is hygroscopic — it absorbs moisture, which may corrode engine parts,” he explains.

But Ravikrishna says manufacturers have followed BIS standards to produce ethanol-compliant vehicles since the blending programme began in the early 2000s. He added that any minor fuel efficiency loss or gasket wear in older vehicles can be addressed through regular maintenance and simple part replacements.

Professor Shanmukha Nagaraj, head of mechanical engineering department, R V College of Engineering, says in their lab tests, they have experienced cranking and detonation (knocking) sounds from the use of EBP. But that could also be due to inadequate testing infrastructure —“How ethanol is extracted makes a lot of difference,” he explains. “We reported a fuel inefficiency of 4-8%, but emissions surely came down by 10-12%,” he adds. 

What consumers can do 

Consumer rights activist Y G Muralidharan said citizens can file RTIs seeking government studies on the impact of ethanol-blended petrol. He questioned the fairness of paying full price for fuel that may contain only 80% petrol, and called for clarity on warranty concerns related to non-compatible vehicles. He also urged clear labelling of ethanol-blend dispensers at fuel stations, and for pure petrol to remain available as an option. Prof T V Ramachandra says vehicle users can approach BioFuel Board in the state to request further testing.