Amid the ongoing debate over ethanol-blended petrol, Union Road Transport and Highways Minister Nitin Gadkari said vehicle owners cannot accurately measure their car's fuel efficiency on their own and should instead rely on tests conducted using authorised dealer equipment.
Gadkari made the remarks during an interview with ABP News on Monday while responding to a journalist who claimed her car's mileage had dropped significantly after switching to the government's E20 petrol.
The journalist said her car, purchased in 2023 and believed to be E20-compatible, had seen its fuel efficiency decline from around 11 km per litre to 7 km per litre during city driving.
When Gadkari asked how the mileage had been calculated, she replied that she had relied on her vehicle's dashboard display, as most drivers do.
Responding to this, Gadkari reiterated that accurate fuel economy cannot be determined by individual users.
"You and I can't check the mileage. A car's mileage can only be checked using a company-authorised dealer's machine," he said.
The exchange comes days after the Centre acknowledged that E20 petrol can reduce fuel efficiency by 3–5 per cent in some vehicles, while continuing to defend the ethanol-blending programme.
Last week, the Ministry of Petroleum and Natural Gas released a question-and-answer document addressing concerns surrounding the Ethanol Blended Petrol Programme. The ministry accepted that E20 fuel may lower mileage in certain vehicles but argued that fuel economy is only one aspect of vehicle performance.
"It is true that in some vehicles there may be a 3–5 per cent reduction in fuel economy. But mileage is only one parameter," the ministry stated.
The government made E20 petrol available nationwide from April 1 as part of its strategy to increase ethanol blending, reduce dependence on imported crude oil and lower emissions.
However, the rollout has drawn criticism from motorists and sections of the automobile industry. Several vehicle owners have reported reduced mileage, while some manufacturers have expressed concerns about the performance of E20 fuel in older vehicles.
Can drivers measure mileage themselves?
Not with absolute precision, but they can obtain a reasonably reliable estimate.
Modern vehicles calculate fuel economy using information such as the amount of fuel injected into the engine, the distance travelled and data processed by the engine control unit (ECU). Dashboard fuel economy figures are estimates but are generally considered to be within 2–5 per cent of manual calculations over a full tank, depending on the vehicle.
Automotive experts widely regard the full-tank method as the most dependable way to assess real-world fuel efficiency. The method involves filling the fuel tank completely, resetting the trip meter, driving normally until the next refill and then dividing the distance travelled by the amount of fuel required to refill the tank.
What does a dealer's diagnostic machine do?
An authorised dealer's diagnostic equipment performs functions beyond displaying fuel economy.
It accesses detailed information from the vehicle's ECU to check whether systems such as fuel injectors, oxygen sensors and airflow sensors are operating correctly. It can also identify engine faults and verify ECU calibration that may influence fuel consumption.
However, such equipment does not directly measure real-world mileage under all driving conditions.
Actual fuel efficiency is influenced by several factors, including traffic conditions, city or highway driving, air-conditioner usage, tyre pressure, driving habits and the overall load carried by the vehicle.
Assessing Gadkari's statement
In practical terms, a vehicle's onboard fuel economy display provides a useful estimate of mileage, while the full-tank method offers a reasonably accurate measure of real-world fuel efficiency.
Dealer diagnostic tools are primarily intended to detect mechanical or electronic issues that may affect fuel consumption rather than serving as the only valid method for determining a vehicle's mileage.
