E20 (20% ethanol blended with petrol) became mandatory in India since April 2025, as part of a policy to encourage the manufacture of bio-ethanol (from sugarcane, maize, or rice), and reduce the import of petroleum. However, it sparked a range of protests and litigations around its impact on vehicle mileage and maintenance by daily users, experts, and automakers.
Here we analyse the main concerns, and how your household can budget for this shift in fuel policy.
E20's Effect on Vehicle Performance
Ethanol has lower energy value than petrol, meaning more fuel containing ethanol has to be burned to deliver the same power as 100% petrol (E0), lowering your vehicle's overall fuel efficiency. In flex-fuel or optimized engines, which are the standard in vehicles made in 2023 or later, some of this loss is offset, but in non-adapted cars the drop is visible — between 2–4 % reduction in mileage.
Parameter | E20 | E0 |
| Composition | 80% petrol + 20% ethanol | 100% petrol |
| Energy Value | 26 Megajoules/kg | 42 Megajoules/kg |
| Mileage | ~2–4% mileage drop vs E0 | Baseline |
| Octane Rating (indicating smoother combustion) | 95–97 RON | 91–94 RON |
| Engine Compatibility | Requires E20-ready engines or ethanol-resistant components (fuel lines, seals, injectors) | Compatible with all petrol vehicles |
| Moisture Absorption (hygroscopy) | Absorbs water causing ethanol & petrol to separate (phase separation) | Minimal |
| Corrosion Risk | Higher | Lower |
| Cold Start Behaviour (Engine Hesitancy) | Harder in cold or humid conditions due to higher vaporisation heat of ethanol | Better |
| CO₂ & CO Emissions | Lower | Higher |
| Aldehyde Emissions | Higher | Lower |
| Cost per Litre | Cheaper at pump due to ethanol subsidy | Slightly more expensive |
| Fuel Economy (km/l) | 2–4% lower mileage in non-flex engines | Higher mileage and range |
| Maintenance Impact |
| Standard maintenance schedule |
| Environmental Impact | Renewable, reduces fossil fuel use | Higher carbon footprint |
Consequences and Concerns
| Higher fuel bills per km | Because of lower energy content, households must buy more volume to cover the same distance, raising per-km fuel cost. |
| Labelling |
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| More frequent repairs & maintenance | Experts have warned that while short-term impacts might be minimal, long-term cumulative wear—especially in older or low-specification engines—could escalate costs. Replacing fuel filters, O-rings, seals, injectors or rubber hoses may become necessary earlier than expected, especially in older cars. |
| Uncertainty of warranty & insurance | Some vehicle owners worry whether using E20 might void warranties or insurance, though the government has clarified that legitimate use of mandatory blends will not void coverage. |
| Food vs fuel tradeoffs | In India, diverting grains (rice, corn) to ethanol production can raise food prices or reduce availability, indirectly affecting household budgets. |
| Incentives for switching to new cars | Experts have suggested that the government offer incentives to encourage users to shift to cars made after 2023 that have adaptations for E20, such flex-fuel engines, electronic fuel injection (EFI), etc. |
How Should I Budget for the Future?
| Allow a buffer for 3–5 % extra fuel cost |
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| Plan for incremental maintenance costs | If your car isn't much older than 2023 (pre-EFI), keep aside a small fund as your car's filters, rubber hoses, injectors may need repairs or replacement earlier than their usual lifespan. |
| Consider upgrade kits | If your car is already a few years old, you may consider
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| Behavioural changes |
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| Monitor pump practices | Stick to fuel stations that have good reviews, and are known to clearly display blend labels. Avoid pumps suspected of fuel adulterations where possible. |
| Buy ethanol-ready vehicles |
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Before We Go
Older engines are expected to struggle with cold starts, phase separation leading to potential corrosion of fuel lines, deterioration of rubber seals, deposits in the pipes, and rough running. Users are already reporting performance losses, and increased maintenance, even though experimental studies have shown that the declines in torque and power are statistically small (<2%) in well-managed engines. But for real-world use over many thousands of kilometers in varying conditions, concerns have not been allayed.
In practical terms, if you own a car older than 2023, be prepared for a small drop in efficiency, and plan for additional maintenance. When feasible, migrate to electric vehicles, or ethanol-resilient ones. Meanwhile, make sure of clear pump labeling, maintain good driving practices, and keep an eye on evolving vehicle standards.
Keywords: ethanol-blended petrol, E20 impact on mileage, vehicle corrosion from ethanol, fuel efficiency loss ethanol, long-term engine wear ethanol, household fuel budget planning, ethanol mandate effects, older car ethanol compatibility, biofuel petrol India, domestic budgets fuel costs
