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, but the government is planning to soon start distributing E85 and E100 fuels for flex-fuel vehicles. 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's 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 fueling 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 fueling 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 alleviate the country's expenditure on imported oil, though this is dependent on adoption, which itself requires good incentives and policies to be driven. Ethanol has a high octane rating (around 100-110 RON) as well, 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 vapor helps prevent knocking.
Since ethanol burns cleaner than petrol, E85/E100 fuels also significantly cut tailpipe emissions like carbon monoxide (CO), 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, to be specific. 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.
Will E85 and E100 fuels cost less than petrol?
Claimed to significantly undercut petrol
Yes, the government has confirmed that since ethanol is produced within India, E85 and E100 will be priced substantially lower than petrol. Exact pricing details, however, remain under wraps. It should also be noted that 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 4-wheeler side, industry experts tell us that engineering a petrol car to run on E85/E100 can cost about Rs 50,000-1 lakh.
What will the availability of E85 and E100 fuels be like?
Current target is 5,000 dispensing stations in major cities by end-2027
According to petroleum minister Hardeep Singh Puri, the government will start off by installing 50-100 ethanol dispensing stations in the Delhi-NCR and Mumbai-Pune-Nagpur corridor, which will expand 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.
Dipan Sur
Uday Singh
Saptarshi Mondal
