Explained: Why is India moving to RON 95 alongside E20 petrol?

India will begin nationwide supply of petrol blended with up to 20% ethanol from April 1, 2026, marking a major milestone in its biofuel programme. In a notification issued on February 17, the Ministry of Petroleum and Natural Gas directed oil marketing companies to supply petrol containing up to 20% ethanol that also meets a minimum Research Octane Number (RON) of 95.

This effectively makes E20 with RON 95 the new petrol standard across the country. The move comes after concerns emerged during the early rollout of E20 regarding fuel efficiency, engine roughness and performance inconsistencies in some vehicles.

India has steadily scaled up ethanol blending over the past decade as part of its strategy to reduce dependence on imported crude oil and cut vehicular emissions. The country achieved 10% blending in 2022 ahead of schedule and subsequently advanced its 20% blending target from 2030 to the 2025–26 supply year. As E20 fuel began reaching retail pumps in phases from 2023 onwards, some consumers  particularly owners of older BS4 and early BS6 petrol vehicles  reported lower mileage, hesitation under load and changes in responsiveness.

While ethanol blending was the visible change, the underlying issue was more structural. India was introducing higher ethanol content into a fuel ecosystem still built around roughly 91 RON petrol, which is lower than the 95 RON baseline commonly used in many global markets. Ethanol alters combustion dynamics by influencing pressure and ignition timing inside the engine. When blended into lower-octane petrol, it can increase the likelihood of unstable combustion under certain operating conditions.

Addressing efficiency concerns

In such situations, modern engine control systems respond by retarding ignition timing to prevent knocking and protect the engine. While this safeguards durability, it can also reduce performance and worsen real-world fuel efficiency. This was one of the key reasons behind the mileage concerns that surfaced during early E20 adoption.

The introduction of RON 95 alongside E20 is intended to stabilise combustion as ethanol content rises. RON, or Research Octane Number, measures a fuel’s resistance to knocking. Higher octane fuel burns more smoothly under pressure and allows engines to maintain optimal ignition timing instead of compensating for instability.

In practical terms, this reduces the likelihood of engines detuning themselves in response to fuel behaviour. As a result, the mileage impact of ethanol blending may move closer to its expected theoretical levels rather than the sharper drop some users reported earlier.

Aligning fuel with modern engines

Globally, ethanol blending is typically paired with higher octane fuels. India’s earlier approach created a mismatch, as many modern engines including turbocharged and direct injection units are calibrated around higher octane fuel standards.

Moving to E20 with RON 95 brings India’s fuel roadmap closer to the technological direction of newer internal combustion engines and hybrid-ready powertrains, which benefit from combustion stability.

From April 2026, petrol pumps across India will supply E20 fuel meeting the RON 95 standard, with the notification allowing limited flexibility in specific regions where supply constraints may arise. Most vehicles manufactured in recent years are already designed to run on E20, and the higher octane fuel is expected to support smoother integration as ethanol blending becomes the norm.

The move reflects an effort to address real-world usability concerns while continuing the broader transition toward ethanol-blended fuel, ensuring that higher renewable content is supported by improved fuel quality.