Union minister Nitin Gadkari has stirred a fresh debate on ethanol-blended fuel. He says ordinary car owners cannot correctly measure their vehicle’s mileage. Only a dealer’s machine can do that, he claims. This has left many drivers confused. If they can’t trust their own numbers, how have they been tracking fuel efficiency all these years?
What Gadkari actually said
In a television interview, Gadkari was asked about falling mileage after the switch to E20 petrol. A journalist told him her car’s city mileage had dropped sharply, from 11 km per litre to 7 km per litre. Gadkari pushed back. He asked how she had arrived at that number. When she said she read it off her car’s dashboard, like most people do, he dismissed the method. He said real mileage can only be confirmed on equipment used by authorised company dealers.
This exchange is part of a wider row. The government rolled out E20 petrol across the country from April 1. E20 is petrol mixed with 20 percent ethanol. The goal is to cut India’s oil import bill, support farmers, and lower vehicle emissions. But soon after the rollout, many drivers began reporting lower mileage. Some car makers also flagged concerns, especially for older vehicles not built for higher ethanol content.
Even the government admits a drop
Interestingly, the Ministry of Petroleum and Natural Gas has already accepted that E20 can hurt fuel efficiency. In an official clarification document released last week, the ministry said some vehicles may see a 3 to 5 percent drop in mileage. It added that mileage should not be viewed as the only measure of a fuel’s worth.
So how do drivers normally check mileage?
Most car owners rely on one of two simple methods, and both have been used for decades, long before dashboard computers existed.
The dashboard readout. Nearly every modern car shows an estimated mileage figure on its instrument panel. This number is not a guess. It comes from the engine control unit, which tracks how much fuel is injected and how far the car travels. According to automotive experts, this onboard estimate is usually within 2 to 5 percent of a manually calculated figure over a full tank.
The full-tank method. This is the method mechanics and enthusiasts trust most. A driver fills the tank completely, resets the trip meter to zero, and drives normally until the tank needs filling again. At the next refill, they divide the distance covered by the litres of fuel added. This gives a real-world figure based on actual driving, not a lab estimate.
Both methods have been standard practice for years. They don’t need a dealer’s workshop or special diagnostic tools.
What a dealer’s machine actually does
A manufacturer’s diagnostic tool is a different kind of device altogether. It plugs into the car’s onboard computer and checks health of parts like fuel injectors, oxygen sensors, airflow sensors. It can flag engine faults and confirm whether ECU is calibrated correctly. This is useful for spotting mechanical problems that might be quietly hurting fuel economy.
But here’s the catch: this machine does not measure real-world mileage as the car is actually driven day to day. It cannot account for traffic jams, city versus highway routes, air-conditioner use, tyre pressure, how heavy the car is loaded, or a person’s driving habits. All of these affect mileage far more than any single test on a workshop machine ever could.
In short, dealer equipment is built to diagnose faults, not to serve as the only trustworthy mileage check.
Weighing Gadkari’s claim against the facts
Independent studies back up the idea that E20 does reduce mileage to some extent. A 2021 roadmap by NITI Aayog estimated a 6 to 7 percent drop in fuel economy for older, E10-compatible cars running on E20, and a smaller 3 to 4 percent drop even in cars tuned specifically for E20. This lines up with the government’s own recent admission of a 3 to 5 percent loss.
On engine damage, there’s no solid evidence that E20 harms vehicles designed or certified for it. That said, the same NITI Aayog roadmap warned that older cars might need rubber, plastic, and other components replaced, since ethanol is more corrosive than pure petrol.
On testing, government records show the fuel underwent evaluation by agencies including ARAI, Indian Oil, and SIAM before the phased rollout began.
On whether drivers can judge mileage on their own, the picture is mixed. Single dashboard glance or short drive can be misleading because lab conditions rarely match real roads. But full-tank method, repeated over time, is widely accepted by experts as fair and practical way to estimate real mileage.
Finally, there is also no large-scale documented evidence of E20 causing widespread engine failures across India. Even so, complaints and legal petitions have raised compatibility concerns for older cars, and some manufacturers have set lower ethanol limits for earlier models in their manuals.