E20 ethanol shift hurts older Indian cars mileage

The Hidden Toll of E20 on BS4 Cars

Look, the move to E20 petrol isn’t just a policy tweak. It could mean less mileage for people still driving older BS4 machines. The tests on models like the Maruti Dzire, Hyundai Grand i10, and Volkswagen Polo GT show a measurable drop in fuel efficiency when switching from the standard E10 blend to E20. No dramatic numbers were shared in the piece, but the trend is clear: these older engines aren’t optimized for higher ethanol content. And that matters because most households don’t swap cars every few years. It’s your daily ride, your fuel bills, your routine.

So what does this mean for you? If you’re clinging to a BS4 car, this isn’t just “next year’s problem.” It’s real on your pump today. Newer cars are engineered to handle higher ethanol without losing mileage, but older vehicles aren’t built for the shift. The result is a quiet, personal impact: higher fuel costs, more trips to the pump, and a bit more frustration on those long commutes.

Here's the thing: you don’t have to accept surprise drops in efficiency. The evidence from those models is a nudge, not a verdict, but it’s a nudge you can act on.

Why Older BS4 Engines Struggle

Ethanol carries less energy per liter than petrol, so more ethanol can mean you burn more litres to go the same distance. That logic translates into real-world mileage gaps when you move from E10 to E20. But energy content isn’t the only factor. Older fuel systems—hoses, seals, and certain alloys—aren’t always ethanol-ready, and the engine control units (ECUs) in BS4-era cars aren’t tuned for the higher blend. In short, the hardware and the software aren’t in sync with E20.

Newer cars, on the other hand, come with calibrations and materials designed for higher ethanol mixes. They anticipate the extra burning, adjust timing, and keep fuel delivery steady. For your everyday life, that translates to a smoother experience and, crucially, a more predictable fuel bill.

The bigger implication is simple: as India pushes for higher ethanol blends, the real winners are drivers who align their cars with the fuel they’ll actually use. Your choice tomorrow could save you thousands of rupees over the next year. The road ahead isn’t just about greener fuel—it's about smarter choices for the car you already own.