After the uniform and mandatory rollout of 20% ethanol blended petrol across India, commonly known as E20, the Indian government is likely to mandate the isobutanol blending in diesel by the end of this year. V Umashankar, Secretary at the Ministry of Roads, Transport and Highways (MoRTH), has said that the government is likely to bring a mandate on blending isobutanil with diesel as early as this year to improve energy security in the country and decarbonise the road and highways sector.
Currently, petrol across India is sold with 20% ethanol blended since April 2025. The country achieved the target of E20 well ahead of the original deadline. Now, with the plan to blend isobutanol in diesel, the Indian government believes that since diesel consumption is almost twice that of petrol, the isobutanol blending will have a far greater impact on India’s energy security than ethanol blending in petrol.
PTI has quoted Umashankar as saying that blending of diesel has been looked into with great seriousness. “Bharat Petroleum is already undertaking strategic research for isobutanol blending with diesel. And the results are very encouraging. It is quite likely that the blending mandate will start coming in somewhere later this year,” he reportedly said.
The transport secretary also reportedly said that the blending programme, which has taken off in the last 10-12 years, is further being expanded, and the MoRTH has issued a draft notification for E85, a blend of 85% ethanol with petrol. “There have been some concerns about blending at the lower level (E20), but here it is a little different because the vehicle is manufactured differently. It will have a separate fuel dispenser also at the petrol pumps for dispensing E85 or E100 fuel, unlike normally blended petrol, which is done through a common dispenser,” Umashankar said.
How will a diesel-isobutanol blend impact diesel cars?
To understand how the diesel-isobutanol blend will impact the diesel vehicles, first we need know what is isobutanol and how its blending is different from ethanol blending with petrol.
What is isobutanol?
Isobutanol is an alcohol-based fuel that can be blended with diesel, just like how ethanol is blended with petrol. Isobutanol has a higher energy density compared to ethanol, which means the diesel engine-propelled vehicles will see a smaller fuel efficiency drop when they run on isobutanol blended diesel. The isobutanol can be produced from agricultural feedstocks, including sugarcane and biomass, which means it could be connected to the same domestic supply chains being built for the ethanol programme across India.
isobitanol blending in diesel: What you must know
Diesel is chemically different fuel from petrol and blending anything into it requires different level of engine tolerances as well as com(patibity considerations. While the petrol engines running on ethanol-blended fuel for years without major consequences, diesel engines, especially the older ones, can be highly sensitive to the changes in fuel composition. The reason behind this is that diesel ignites through compression rather than a spark, the opposite of petrol engines’ operational process. The fuel chemistry in diesel plays a more direct role in combustion timing and efficiency than petrol.
This is the reason why government moved more cautiously on diesel-isobutanol blending, as compared to ethanol blending in petrol. The research currently underway at Bharat Petroleum is specifically focused on ensuring that isobutanol-diesel blends meet the combustion and lubricity requirements of the existing diesel engines powering the vehicles on the Indian road.
Isobutanol-blending in diesel: Should you be worried?
If you are a diesel vehicle owner, it is legitimate to be concerned about the isobutanol blending in diesel that is likely to be implemented by the end of this year. An isobutanol-diesel blend generally causes a slight reduction in fuel efficiency and engine power, but it also produces lower particulate emissions. With the possible low initial blend rates (up to 10%), the isobutanol-blended diesel would be safe and more engine-friendly than ethanol-blended petrol. If the blending is low, your diesel vehicle is unlikely to require any major modifications.
Aso, it is noteworthy that the diesel vehicles most directly to be impacted are the trucks, buses, tractors, etc. Passenger vehicle segment in India has been witnessing gradually declining share of diesel models over the last several years. For the diesel vehicle owners, the key concern will be compatibility. The Indian government is yet to indicate what would be the initial blend percentage. However, if it starts at typically in the 5-10% range, before scaling up, there should not be much to worry for owners of relatively new diesel vehicles. However, the fleet operators and old diesel vehicle owners will have legitimate concern.
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