Over the past few years, the government has been increasingly eyeing ethanol blending as a relief from steep fuel import bills, exacerbated by the West Asia conflict in recent memory. There’s already 20 percent ethanol blending in petrol (E20) as the baseline since April 2025, and in June 2026, the government introduced E85 for flex-fuel vehicles; E100 is expected to be offered in the near future too. Below, we’ve answered every question you may have surrounding E85 and E100.
What are E85 and E100 fuels?
Ethanol comprises the overwhelming majority of the blend
As the name suggests, E85 and E100 are fuel blends with very high percentages of anhydrous (zero water) ethanol. E85 is 85 percent ethanol and 15 percent petrol, while E100 is 93-95 percent ethanol mixed with 5-7 percent of petrol and other solvents – the latter helps during cold-starts (especially at low temperatures), prevents freezing, and should there be a fire, the petrol gives the flame a visible colour.
It should also be made clear that E20-compliant vehicles cannot run on E85/E100 without significant hardware changes and additions. The vast variance in ethanol content between E20 and E85/E100 effectively makes them different fuel types.
What changes does a vehicle need to support E85 and E100 fuels?
Fuel system needs higher-flow and corrosion-resistant components
First up is the fuel system. Since ethanol’s energy per volume is lower than petrol’s, flex-fuel engines need around 30-40 percent more fuel to develop the same amount of power. This often requires a high-flow fuel pump and larger injectors. Fuel lines, seals, regulators and tanks must also be ethanol-resistant – ethanol is hygroscopic in nature, which means it can absorb moisture from the air and corrode whatever it is in contact with.
Ethanol content sensor helps ECU adjust for varying ethanol blends
An ethanol content sensor is also required for flex-fuel powertrains. As its name suggests, the sensor measures ethanol content in the fuel and feeds real-time data to the ECU to adjust fuelling for optimal engine operation. Speaking of which, the fuel maps in the ECU will also need richer injection (higher fuel-to-air ratio) to compensate for ethanol’s lower energy density, and ignition timing may be advanced thanks to ethanol’s high octane rating. Cold-start fuelling must also be adjusted (often drastically richer) as ethanol blends vaporise poorly when cold.
What are the pros and cons of E85 and E100 fuels?
Reduced dependence on oil imports, better performance and lower emissions
Starting off with the pros, higher ethanol blends help lower the country’s spending on imported oil, though this is dependent on adoption, which is enabled by good incentives and policies. Moreover, ethanol has a high octane rating of around 100-110 RON, allowing for more aggressive tuning. Engines running E85 or E100 can advance ignition timing and/or boost to make more power, and the added cooling effect of ethanol vapour helps prevent knocking.
Since ethanol burns cleaner than petrol, E85/E100 fuels also significantly cut tailpipe emissions like carbon monoxide (CO), nitrogen oxides (NOx) and unburned hydrocarbons. However, they give rise to a different type of hazardous air pollutant: acetaldehyde (C2H4O).
Considerable drop in fuel efficiency
This is where we come to the cons, the biggest of which is fuel efficiency. Since ethanol has a lower energy density, fuel consumption of vehicles running E85 is significantly higher – 20-30 percent more than that of petrol. E100 is worse in this regard, with a fuel efficiency loss of around 35 percent over petrol. This means you’ll be filling up more often if you drive a flex-fuel vehicle.
Do E85 and E100 fuels cost less than petrol?
E85 priced at roughly Rs 20/litre below petrol
Yes, E85 is a fair bit cheaper than petrol at Rs 82.12/litre in Delhi – a difference of around Rs 20/litre. Since E100 features higher ethanol content than E85, expect it to be priced even lower. That said, engineering for E85/E100 compliance carries costs that are passed on to the consumer. For instance, the Hero Splendor+ Flex Fuel commands a Rs 5,153 premium over its petrol counterpart. On the four-wheeler side, industry experts tell us that engineering a petrol car to run on E85/E100 can raise its cost by about Rs 50,000-1 lakh.
What is the availability of E85 and E100 fuels like?
Current target is 5,000 dispensing stations in major cities by end-2027
In June 2026, the very first E85 dispensing station was inaugurated on Pusa Road, New Delhi. According to petroleum minister Hardeep Singh Puri, initial plans include 50-100 E85/E100 dispensing stations in the Delhi-NCR and Mumbai-Pune-Nagpur corridor, expanding to 500 stations by December 2026. Puri estimates that as many as 5,000 dispensing stations will be set up across major Indian cities by the end of 2027.