After Centre admits E20 may reduce mileage, Nitin Gadkari says car owners can’t check fuel efficiency accurately
Union Road Transport and Highways Minister Nitin Gadkari on Tuesday claimed that the car owners cannot accurately measure their vehicle’s fuel efficiency on their own and should instead rely on tests conducted using manufacturer-authorised diagnostic equipment.
Amid growing concerns over the impact of E20 petrol on mileage, the Union Minister appeared in an interview with ABP news.
His statement comes in response to a journalist’s question that her car’s fuel economy had dropped significantly after switching to government-mandated E20 petrol. The journalist said the mileage of her E20-compatible car, purchased in 2023, had fallen from around 11 kmpl to 7 kmpl during city driving. When asked how she had measured the mileage, she replied that she had relied on the car’s dashboard display. “You and I can’t check the mileage. A car’s mileage can only be checked using a company-authorised dealer’s machine,” Gadkari said.
The remarks come just days after the Centre acknowledged that E20 petrol can reduce fuel efficiency in certain vehicles.
Last week, the Ministry of Petroleum and Natural Gas released a question-and-answer document addressing concerns surrounding the Ethanol Blended Petrol (EBP) Programme.
The ministry admitted that E20 petrol may reduce fuel economy by around 3-5% in some vehicles, while maintaining that mileage should not be viewed as the sole measure of the fuel’s effectiveness. “It is true that in some vehicles there may be a 3-5% reduction in fuel economy. But mileage is only one parameter,” the ministry said.
The Centre made the sale of E20 petrol mandatory across India from April 1 as part of its strategy to reduce crude oil imports, increase ethanol blending and lower vehicular emissions.
The rollout, however, has drawn criticism from several motorists, many of whom claim they have experienced a noticeable decline in mileage. Some automobile manufacturers have also raised concerns about the performance of E20 fuel in older vehicles.
While Gadkari said only dealer-authorised equipment can accurately determine mileage, automotive experts say drivers can still obtain a fairly reliable estimate using commonly accepted methods.
Modern vehicles calculate fuel economy using information from the engine control unit (ECU), including fuel injection data, distance travelled and engine performance. Dashboard mileage figures are estimates but are generally considered reasonably accurate, often falling within 2-5% of manual calculations over a full tank.
Experts widely regard the full-tank method as the most reliable real-world way to measure fuel economy. Under this method, drivers fill the fuel tank completely, reset the trip meter, drive normally until the next refill, refill the tank and divide the distance travelled by the litres of fuel added.
Manufacturer-authorised diagnostic tools serve a different purpose. They access detailed ECU data to check whether components such as fuel injectors, oxygen sensors, airflow sensors and engine calibration are functioning correctly. These systems help identify mechanical or electronic issues that may affect fuel consumption but do not directly measure real-world mileage under all driving conditions.
Fuel efficiency also depends on several external factors, including traffic conditions, city versus highway driving, tyre pressure, air-conditioner usage, driving style and vehicle load.
As a result, experts say a vehicle’s onboard display and the full-tank method remain practical ways for motorists to estimate real-world mileage, while dealer diagnostic equipment is primarily intended to diagnose faults that could affect fuel economy.