The price on the pump display tells you the cost per litre. But litres are not what you buy — you buy kilometres. E20 has changed the relationship between litres and kilometres, which means the real cost of driving is different from what the pump price suggests. This article shows you how to calculate your true cost per kilometre, why it matters, and what the numbers look like for different vehicle types.
Why cost per litre is misleading
When the government or oil marketing companies (OMCs) discuss fuel prices, they talk about ₹ per litre. When you fill up, the pump shows ₹ per litre. Media headlines report price changes in ₹ per litre.
But as a driver, what matters is the cost of getting from A to B — the cost per kilometre. This is the metric that determines how much you actually spend on transport each month.
Cost per kilometre = Fuel price per litre ÷ Mileage (km/L)
If E20 costs the same per litre as E10 but delivers fewer kilometres per litre, the cost per kilometre has increased — even though the pump price looks the same. This is not a hypothetical. Ethanol has roughly 33 percent less energy per litre than petrol. A 20 percent ethanol blend (E20) contains about 6.5 percent less energy per litre than pure petrol (E0). In practice, real-world mileage losses vary from 5 to 15 percent depending on the vehicle, driving conditions, and how the engine management system compensates.
The cost-per-litre framing hides this energy loss. It treats all litres as equal when they are not. A litre of E0 and a litre of E20 contain different amounts of energy, and therefore deliver different amounts of driving range.
A worked example
Consider a typical commuter motorcycle in Delhi. Before E20 (when E10 was the norm), the rider achieved 45 km/L. After the shift to E20, with a typical 11 percent mileage loss, the same bike delivers 40 km/L.
| Metric | E10 (before Apr 2026) | E20 (after Apr 2026) |
|---|---|---|
| Fuel price (Delhi) | ₹96.51/L | ₹102.12/L |
| Mileage | 45 km/L | 40 km/L (11% drop) |
| Cost per km | ₹2.14/km | ₹2.55/km |
| Effective price increase | — | 19.2% |
The pump price went up 5.8 percent (₹96.51 to ₹102.12). But the cost per kilometre went up 19.2 percent because you are paying more per litre and getting fewer kilometres per litre. The headline price increase understates the real increase in driving cost by a factor of three.
This is the core of the cost-per-km argument. The pump price and the driving cost have diverged. Anyone who looks only at the pump price is underestimating what they actually pay.
How to calculate your cost per km
You need two numbers:
- Your actual mileage (km/L). Use the fill-to-fill tracking method to measure this accurately. Do not use the manufacturer’s claimed figure — use your real-world number.
- The fuel price you paid (₹/L). This is on your fuel receipt or the pump display.
Formula: Cost per km = Price per litre ÷ Mileage (km/L)
Example: ₹102 ÷ 40 km/L = ₹2.55 per km
The fill-to-fill method
For an accurate mileage measurement, fill your tank completely at a pump. Note the odometer reading. Drive normally until you need to refuel. Fill completely again. Note the new odometer reading and the litres filled.
Mileage = (New odometer − Old odometer) ÷ Litres filled
Do this for at least 5–10 tankfuls to get a reliable average. Single-tank measurements are noisy because driving conditions, traffic, weather, and route vary. The average over many tanks is your real mileage.
Cost per km by vehicle type
Different vehicles have vastly different mileage, which means vastly different cost-per-km numbers. The table below covers the major categories of vehicles on Indian roads, using approximate real-world mileage on E20 and a fuel price of ₹102/L.
| Vehicle type | Typical E20 mileage | Cost per km (at ₹102/L) | Monthly cost (typical usage) |
|---|---|---|---|
| Scooter (110cc) | 42–48 km/L | ₹2.13–2.43 | ₹1,700–1,943 (800 km) |
| Commuter bike (125cc) | 40–50 km/L | ₹2.04–2.55 | ₹1,632–2,040 (800 km) |
| Sport/street bike (150–200cc) | 35–42 km/L | ₹2.43–2.91 | ₹1,943–2,331 (800 km) |
| Cruiser/touring bike (350cc+) | 25–32 km/L | ₹3.19–4.08 | ₹2,550–3,264 (800 km) |
| Auto-rickshaw (petrol) | 24–30 km/L | ₹3.40–4.25 | ₹5,440–6,800 (1,600 km) |
| Hatchback car | 14–18 km/L | ₹5.67–7.29 | ₹8,500–10,929 (1,500 km) |
| Sedan/compact SUV | 10–14 km/L | ₹7.29–10.20 | ₹10,929–15,300 (1,500 km) |
| Full-size SUV (petrol) | 7–10 km/L | ₹10.20–14.57 | ₹15,300–21,857 (1,500 km) |
Mileage ranges are approximate real-world figures on E20. Monthly costs assume 800 km for two-wheelers and 1,500 km for cars. Actual figures vary with driving conditions, vehicle age, and maintenance.
Annual cost projections
Monthly numbers feel manageable. Annual numbers reveal the true scale. Here is what the E20 mileage penalty costs different vehicle owners over a full year, assuming a 10 percent mileage drop from E10 to E20:
| Vehicle type | Annual km | Extra litres/year (E20 vs E10) | Extra annual cost (at ₹102/L) |
|---|---|---|---|
| Commuter bike (45 km/L E10) | 10,000 | 25 L | ₹2,533 |
| Sport bike (38 km/L E10) | 8,000 | 23 L | ₹2,381 |
| Auto-rickshaw (30 km/L E10) | 24,000 | 89 L | ₹9,067 |
| Hatchback (16 km/L E10) | 15,000 | 104 L | ₹10,625 |
| Sedan/SUV (12 km/L E10) | 15,000 | 139 L | ₹14,167 |
| Ride-hailing car (12 km/L E10) | 72,000 | 667 L | ₹68,000 |
A personal car owner pays ₹10,000–14,000 more per year. A ride-hailing driver pays ₹68,000 more per year — money that comes directly from their income, not from the platform.
Comparing with alternatives
Once you know your cost per km on E20, you can meaningfully compare it with alternatives. The table below shows typical running costs across fuel and power sources:
| Fuel/power source | Cost per km (car) | Cost per km (two-wheeler) |
|---|---|---|
| E20 petrol | ₹6–10 | ₹2–3 |
| CNG | ₹3.5–5 | N/A (rare) |
| Diesel | ₹4–6 | N/A |
| Electric (home charging) | ₹1–1.5 | ₹0.3–0.5 |
| Electric (public charging) | ₹2–3 | ₹0.5–1 |
On a cost-per-km basis, E20 petrol is the most expensive option for cars and the second most expensive for two-wheelers (after premium petrol, where available). CNG costs roughly half as much per km as E20 petrol for cars. Electric vehicles with home charging cost one-fifth to one-seventh as much per km.
These comparisons explain the accelerating shift toward CNG and EVs among high-mileage users. For a ride-hailing driver doing 200+ km/day, the per-km difference between E20 petrol and CNG translates to ₹4,000–6,000 per month in savings. Over the life of a CNG kit (₹50,000–90,000), the payback period is often under a year.
Reading your fuel receipt
Indian fuel receipts typically show:
- Product: MS (Motor Spirit) — this is petrol. The receipt does not distinguish between E10 and E20.
- Rate: Price per litre (includes all taxes)
- Volume: Litres dispensed
- Amount: Total ₹ charged
- Density: Measured density of the fuel at the pump
What the receipt does not show:
- Ethanol content (E10, E20, or actual percentage). You cannot determine from the receipt what blend you received.
- Energy content per litre
- Tax breakdown (central excise, state VAT, dealer commission)
- Base petrol price before taxes
The tax-on-less-energy problem
The taxes on petrol are substantial. In Delhi, central excise is ₹19.90/L and state VAT is approximately ₹17/L. Roughly 36 percent of the pump price is tax. This tax is charged on the E20 blend — a blend with lower energy content than the E0/E5 fuel the tax rates were originally set for.
In effect, you are paying the same tax rate on a litre that gives you fewer kilometres. The tax per kilometre has increased even if the tax per litre has not. If the government were to tax fuel by energy content (per megajoule, for example) rather than by volume (per litre), E20 would carry a lower tax per litre than E0. No such adjustment has been made.
This matters because fuel tax is a significant revenue source for both central and state governments. In FY 2024–25, the central government collected approximately ₹3.3 lakh crore in excise duty on petroleum products. States collected additional VAT. There is no fiscal incentive for governments to switch to energy-based taxation when volume-based taxation generates more revenue on a lower-energy fuel.
Why cost per km matters more than ever
Before E20, the cost-per-litre number was a reasonable proxy for driving cost. If petrol went up by 5 percent, your driving cost went up by roughly 5 percent. The mileage was stable, so the only variable was price.
E20 broke this relationship. Now two things are changing simultaneously: the price per litre (which went up) and the kilometres per litre (which went down). Using cost per litre alone captures only one of these two changes.
This is why vehicle owners who track their cost per km have a clearer picture of what E20 is costing them. They can see the total effective increase, compare it with alternatives, and make informed decisions about whether CNG conversion, an EV, or simply reduced driving is the right response for their situation.
How to use this number
Once you know your cost per km, you can:
- Budget accurately. Multiply your cost per km by your expected monthly kilometres to get your true monthly fuel expense. This is more accurate than guessing based on “two tanks a month.”
- Compare vehicles. When buying a new or used vehicle, cost per km is a better comparison metric than claimed mileage or fuel-tank size. A car with 12 km/L real-world mileage costs ₹8.50/km on E20. A CNG car at 25 km/kg costs ₹3.20/km. The ₹5.30/km difference on 1,500 km/month is ₹7,950/month.
- Evaluate alternatives. Is a CNG conversion worth ₹70,000? Divide the conversion cost by your monthly savings to find the payback period. At ₹5,000/month savings, the payback is 14 months.
- Support a consumer complaint. If you file a complaint about E20’s impact, a documented cost-per-km increase backed by fill-to-fill mileage logs is specific, quantifiable evidence. “My cost per km increased from ₹2.14 to ₹2.55, a 19.2 percent increase” is far stronger than “fuel seems more expensive.”
The bottom line
The pump price tells you one number. Your cost per kilometre tells you the number that actually matters. Track your mileage, calculate your cost per km, and you will know exactly what E20 is costing you. The answer, for most vehicle owners, is more than the pump price alone would suggest.
Fuel cost is not what you pay per litre. It is what you pay per kilometre. E20 raised both the price per litre and the litres per kilometre. The combined effect is a real cost increase that is significantly larger than the headline pump-price change. Know your number. Calculate your cost per km. That is the true price of E20.