How to Track Your Mileage on E20: A Step-by-Step Guide

If you suspect E20 is costing you more fuel, the only way to know for certain is to measure it. Anecdotal impressions (“my bike feels slower”) are not evidence. Systematic mileage tracking is. This article explains how to do it properly, what pitfalls to avoid, how to interpret your results, and why those records matter beyond your own curiosity.

The fill-to-fill method

The most reliable way to measure real-world mileage is the fill-to-full method. It is simple, requires no equipment beyond your phone, and gives you data you can trust.

Step by step

1. Fill your tank completely. At the pump, fill until the nozzle clicks off automatically. Do not top off after the click. Note the odometer reading (or reset your trip meter to zero).
2. Drive normally. Do not change your driving style. Drive your usual routes at your usual speed. The goal is to measure your real-world fuel consumption, not an idealised version of it.
3. Fill to full again. At your next fill-up, fill the tank completely again (same pump, same nozzle if possible, to reduce measurement variation). Note the odometer reading and the number of litres pumped.
4. Calculate: Mileage (km/L) = Distance driven (km) ÷ Litres filled.

Example: You drove 320 km and pumped 7.2 litres. Your mileage: 320 ÷ 7.2 = 44.4 km/L.

Why “full to full” works

The fill-to-full method is accurate because it measures the exact volume of fuel consumed between two known fill levels (full). The tank starts full and ends full, so the litres pumped at the second fill equal the litres consumed during the driving period. No estimation, no guesswork about how much fuel was in the tank.

Other methods — estimating from the fuel gauge, using the car’s trip computer, or calculating from partial fills — introduce errors. The fuel gauge is imprecise (the needle moves in steps, not continuously). The trip computer calculates mileage from injector pulse-width data, which can be inaccurate if the injectors are worn or the fuel composition has changed (which is exactly the case with E20). Partial fills make it impossible to know how much fuel was in the tank.

Why you need multiple readings

A single fill-to-fill measurement can be skewed by many factors:

• Traffic conditions: A week of heavy traffic reduces mileage; a week of free-flowing roads improves it.
• Weather: Air conditioning use in summer reduces mileage by 5–15 percent. Headwinds reduce it further. Cold weather affects fuel vaporisation.
• Terrain: Hilly routes consume more fuel than flat routes.
• Passenger load: A car with 4 passengers and luggage uses more fuel than a solo driver.
• Tyre pressure: Low tyre pressure increases rolling resistance and fuel consumption. A tyre that is 5 psi low can increase fuel consumption by 2–3 percent.
• Pump accuracy: Different pumps may have slightly different calibration. The auto-shutoff point can vary between pumps and even between visits to the same pump.

These variations mean a single measurement might show 42 km/L on one tank and 47 km/L on the next, even with the same fuel and driving pattern. The average over at least 5–10 measurements smooths out these variations and gives you a reliable baseline. More data points = more reliable average.

Building a before-and-after comparison

The most valuable mileage data compares your vehicle’s performance on E0/E10 (before April 2026) with its performance on E20 (after). If you have historical records from the E10 era, you already have the “before.”

If you do not have historical data, your current E20 readings still establish a baseline for tracking future changes. You can also compare your measured mileage against the manufacturer’s ARAI-rated figure (adjusted for real-world conditions, which typically means 60–80 percent of the ARAI number). If your measured mileage is significantly below 60 percent of the ARAI rating, something beyond normal real-world adjustment is at play.

A simple tracking template

Sample data for illustration. In this example, mileage dropped from 50.0 km/L (E10) to ~43.9 km/L (E20) — a 12.2% decline.

Tips for accurate measurement

• Same pump, same nozzle. Different pumps may have slightly different auto-shutoff points. Using the same pump and nozzle each time reduces this variable. If you cannot use the same pump every time, at least use the same brand and try to fill at a consistent speed.
• Always fill to click-off. Do not top off after the nozzle clicks. Do not ask the attendant to “round up to ₹500.” Let the nozzle click off naturally each time for consistency. Topping off adds a variable amount of fuel that differs each time.
• Fill at similar temperatures. Petrol expands in heat. A litre of petrol at 45°C is physically larger (takes up more volume) than a litre at 25°C, but contains the same energy. If possible, fill in the morning or evening when temperatures are consistent.
• Drive your normal routes. If you measure on a highway trip and then compare with city driving, the data is meaningless. Keep routes, driving style, and conditions as consistent as possible.
• Note any changes. New tyres, different tyre pressure, change in commute route, extra passengers, heavy rain, AC usage — anything that could affect fuel consumption. These notes help you explain outlier readings later.
• Use the odometer, not the trip computer. In-vehicle mileage displays are estimates based on injector data. The odometer + pump reading is a direct physical measurement and is more reliable. If your vehicle has a trip meter, reset it at each fill-up for convenience, but cross-check against the main odometer.
• Do not skip partial fills. If you partially fill the tank (did not fill to full), skip that measurement and continue tracking from the next full fill. Partial fills break the full-to-full chain and make the calculation inaccurate. Record that you did a partial fill, and note the litres added, but do not calculate mileage for that segment.

Common errors to avoid

• Using the dashboard mileage display: The trip computer’s “average km/L” reading is calculated from injector data, not from actual fuel consumed. On E20, the injectors may deliver fuel at different rates than the computer expects, making the display inaccurate. Trust the pump, not the screen.
• Mixing city and highway data: City driving (with frequent stops, idling, and low speeds) typically gives 30–50 percent lower mileage than highway driving. If you want a meaningful comparison, track city and highway mileage separately or keep your driving mix consistent.
• Too few data points: Drawing conclusions from 2–3 fills is unreliable. Wait until you have at least 5 data points before calculating an average. For a statistically robust comparison (E10 vs E20), you need at least 5 data points on each fuel.
• Ignoring seasonal variation: Air conditioning use in summer can reduce mileage by 5–15 percent for cars (less for two-wheelers without AC). If you compare summer E20 mileage with winter E10 mileage, the AC effect confounds the comparison. Try to compare like with like (summer with summer, or non-AC conditions with non-AC conditions).

How to interpret your results

Once you have 5–10 measurements on E20, calculate the average. Compare it with:

• Your E10/E0 average (if available): A 6–15 percent drop is consistent with E20’s lower energy content. A drop significantly larger than 15 percent may indicate other issues (clogged fuel filter, degraded fuel lines, worn spark plugs) that E20 may have accelerated.
• Your vehicle’s ARAI-rated mileage: Real-world mileage is typically 60–80 percent of the ARAI figure for city driving and 80–95 percent for highway driving. On E20, subtract an additional 5–10 percent from those ranges.
• Other owners of the same vehicle: Online forums (Team-BHP, BikeWale, ZigWheels) often have owner-reported mileage data. Comparing your E20 mileage with others gives you a sense of whether your vehicle is performing normally or has a specific issue.

What to do with your data

For your own awareness

Knowing your actual mileage tells you the real cost per kilometre of driving your vehicle. If your mileage dropped 12 percent after E20, that is 12 percent more fuel cost for the same driving. You can make informed decisions about maintenance, driving habits, or whether CNG conversion or an electric vehicle makes economic sense for your usage pattern.

You can also calculate your annual E20 cost: (E10 mileage − E20 mileage) ÷ E20 mileage × annual fuel spend. For example, if your mileage dropped from 45 to 40 km/L and your annual fuel spend at 40 km/L is ₹25,000, the E20 premium is (45 − 40) ÷ 40 × 25,000 = ₹3,125 per year.

For a consumer complaint

If you plan to file a complaint with your district consumer commission about E20-related mileage loss or vehicle damage, documented mileage records are evidence. A log showing consistent mileage before E20 and a measurable drop after is far more persuasive than “I feel like my bike uses more fuel.”

For a consumer complaint, your mileage log should include:

• Date, odometer, litres, and calculated mileage for each fill-up
• A clear before-and-after comparison (E10 period vs E20 period)
• Consistent driving conditions between the two periods (same routes, same vehicle condition, no other major changes)
• The financial impact calculated from the data: additional litres consumed per month, additional cost per month and per year

See our consumer rights guide for details on filing a complaint.

For an RTI application

Your documented mileage loss supports the basis for an RTI application. “I have documented a 12 percent mileage drop on my vehicle after E20. How many consumer complaints related to E20 mileage loss has the ministry received?” is a stronger RTI question when backed by your own data. Use our RTI template generator to create the application.

For the movement

If thousands of vehicle owners track and share their mileage data, the cumulative evidence becomes impossible to ignore. Your individual records contribute to a body of real-world data that can counter lab-only studies and policy claims. Share your account on the VahanChod platform.

Aggregated data from hundreds of owners of the same vehicle model creates a powerful dataset. If 200 Splendor+ owners report an average 11 percent mileage drop on E20, that is real-world evidence that no lab test can dismiss.

Apps and tools

You do not need a special app. A notebook, a spreadsheet, or a notes app on your phone works fine. The method matters more than the tool.

If you prefer a dedicated tool, several free fuel-tracking apps are available on Android and iOS:

• Fuelio: Free, tracks fill-ups, calculates mileage, shows trends and charts. Popular in India.
• Drivvo: Similar to Fuelio, with expense tracking for maintenance and other costs.
• Google Sheets: A simple spreadsheet with columns for date, odometer, litres, and a mileage formula (=C2/(B2-B1)) gives you a permanent, shareable record.

Whichever tool you use, ensure you can export or share the data. A fuel-tracking app that locks your data inside the app is less useful for complaints or sharing than a spreadsheet you can email.

Measuring your mileage is the simplest thing you can do in response to E20. It costs nothing, takes two minutes per fill-up, and gives you the one thing the policy debate is short on: actual data from your own vehicle. Track it. Know what E20 is costing you. And if you plan to act on it — through a consumer complaint, an RTI application, or a social media post — your records are your evidence.