What does E20 petrol mandate mean for vehicles' fuel efficiency?

From April 2026, the Indian government will mandate the nationwide sale of E20 petrol with a minimum Research Octane Number (RON) of 95. Experts cited in reports warn vehicles made before 2023 may face a 3-7% drop in fuel efficiency because ethanol has lower energy content than petrol. Vehicles manufactured after 2023 are calibrated to run on E20, reports added.