# E20 Petrol Is in Every Tank Now: How to Measure What It Means for Your Own Mileage > Since April 2026, every petrol pump in India dispenses E20. Whether your mileage actually dropped depends on your vehicle and your log. Here is how to measure it properly. Published: 2026-07-17 · Bharometer Blog · https://bharometer.com/blog/e20-petrol-mileage-india-how-to-measure.html Since 1 April 2026, every petrol nozzle at every pump in India is dispensing E20, a 20% ethanol blend. Whether your "kitna deti hai" has changed, and by how much, is not a guess you should be making. It is a number you can measure, fill-up by fill-up. You have almost certainly heard the conversation by now: someone at a chai stall or a parking lot says their mileage "feels" worse since the petrol changed. Someone else says they noticed nothing. Both could be right. Both could be wrong. The problem is that neither of them is working from data. They are working from impressions filtered through traffic variation, tyre pressure, A/C use, and two months of subjective recall. That is not how you find the truth about your own vehicle. The only honest answer to "what did E20 do to my mileage" is a tank-to-tank log kept since the fuel changed. If you have one, you can calculate it. If you do not, you start now and know in three or four fill-ups. ## What E20 Actually Is, and What the Numbers Say E20 is a blend of 20% ethanol and 80% petrol by volume. Since 1 April 2026, all petrol sold at retail pumps in India is E20, minimum RON 95. There is no separate E10 or E0 grade available at the pump. The country hit a 20% average blending rate in 2025, five years ahead of the original 2030 target. Ethanol carries less energy per litre than petrol. That is not a controversy; it is basic chemistry. The practical effect on your fuel economy depends on two variables: how old your vehicle is, and how its engine management was calibrated. Government roadmap estimates put the mileage drop at roughly 1–2% for vehicles designed and calibrated for E20 from the factory, and up to 6–7% for older vehicles calibrated for earlier blends. Controlled test-agency results published in July 2026 measured 2–6% higher fuel consumption versus E10 across 3–10-year-old vehicles, with no engine failures observed in compatible vehicles during long-term trials. To translate that into rupees: on a vehicle averaging 15 km/l before E20, a 5% drop means you now get 14.25 km/l. Over a 1,000 km month, that is roughly 4.7 extra litres consumed. At a petrol price of ₹95/litre, that is about ₹446 extra per month. Not catastrophic, but not nothing either, especially if your vehicle sits in the older, more-affected bracket. Compatibility is the other variable. Petrol vehicles made in India from April 2023 are E20 material-compatible, meaning fuel-system components (seals, rubber hoses, gaskets) are rated for the blend. Vehicles from roughly April 2025 are additionally E20-tuned, meaning the ECU calibration is optimised for the blend, which minimises the mileage penalty. For vehicles older than April 2023, official guidance is that some rubber parts and gaskets may need earlier replacement during routine service. Check your fuel-lid sticker, your owner's manual fuel section, or your manufacturer's service centre with your VIN if you are unsure. ## Why Your Own Measurement Is the Only One That Matters The published ranges (2–6%) are test-bench averages across multiple vehicle models. Your actual result depends on your specific engine tune, your city's traffic pattern, your driving style, how often your A/C runs, and whether you have done a service recently. A vehicle sitting in Mumbai peak-hour traffic on the Western Express Highway burns fuel differently from the same model cruising at 70 km/h on the Pune Expressway. This is why forum posts and WhatsApp forwards are useless for answering your specific question. A mass-market hatchback in Bengaluru is not your CNG-converted car in Lucknow. The only measurement that tells you anything useful is your own tank-to-tank calculation, done consistently. Tank-to-tank is straightforward: fill to the brim, zero your odometer, drive normally, fill to the brim again. Divide kilometers driven by litres dispensed. That is your true mileage for that segment. Do it three or four times and you have a real baseline. The more fill-ups in your log, the more the noise from traffic variation averages out. The problem most people run into is the logging. They fill up, they forget the odometer reading, they guess the litres, or they skip one fill-up and the chain breaks. A broken chain means your tank-to-tank calculation is wrong by definition, because you have no idea what partial fill was left from the previous top-up. ## How to Log a Fill-Up So the Math Always Works At the pump, before you put the nozzle in, note the odometer. After the fill-up, note the litres dispensed and the amount paid. That is three numbers. Log them immediately, before you leave the pump, because you will not remember accurately by the time you get home. The mileage formula is: ``` Mileage (km/l) = km driven since last fill-up ÷ litres dispensed this fill-up ``` For CNG vehicles, the same logic applies but your unit is km/kg, because CNG is priced and dispensed by weight. A dual-fuel vehicle (petrol + CNG) needs separate logs for each fuel type, otherwise the mileage figure is meaningless. Cost per kilometre is the more actionable number for budgeting: ``` ₹/km = amount paid ÷ km driven since last fill-up ``` If you fill ₹1,000 of petrol and cover 180 km before the next fill, your cost per kilometre for that segment is ₹5.56. String several of those together and you have a monthly running-cost picture that no spreadsheet estimate can give you. #### Bharometer Log fill-ups in seconds, get true tank-to-tank mileage and ₹/km automatically: the fastest way to see exactly what E20 is doing in your own vehicle. [Get the App →](https://bharometer.com) ## Reading Your Log: What Counts as a Real Change Once you have three or four fill-ups logged, do not compare individual segments. Traffic noise is too high for a single segment to mean anything. Average your last four entries and compare that average to a baseline average from before April 2026, if you have one. If you do not have a pre-E20 baseline, that is fine. You are establishing a new baseline now. Three months of consistent logging will show you your current average, and you can compare that number to your vehicle's manufacturer-stated fuel efficiency to understand how far off you are running. A mileage drop of 1–2% across adjacent fill-ups is well within normal variation caused by traffic and driving style. Do not read anything into it. A consistent drop of 4–5% across six or more fill-ups, with no change in route or driving pattern, is a real signal worth investigating: a service check (air filter, tyre pressure, fuel injectors) is the first step, not a conclusion about E20 specifically. This matters because E20 is only one of several variables that affect mileage. Tyre pressure alone can move your fuel economy by 2–3%. A dirty air filter can take another 2%. If your mileage dropped after April 2026, that is worth investigating, but the investigation should separate the variables, not assume a single cause. ## CNG and the Dual-Fuel Driver If your vehicle runs on CNG, E20 does not directly affect your CNG mileage. CNG is a different fuel on a different system. But if your vehicle is a dual-fuel setup, petrol is typically used for cold starts and for distances beyond the CNG range. Any E20 effect will show up only in your petrol consumption segments, which is exactly why dual-fuel logs need to stay separate. CNG mileage is measured in km/kg, not km/l. A typical city car on CNG might run 18–22 km/kg depending on the engine and traffic. Log it the same way: odometer at fill, kg dispensed at the CNG station, km covered before the next fill. The math is identical; only the unit changes. Bharometer handles petrol, diesel, CNG (with km/kg mileage), and dual-fuel vehicles in a single log. The pump-scan feature photographs the pump screen and auto-fills litres, amount, and rate, which removes the most common logging error: mistyping numbers in the car park. Since all petrol at Indian pumps is now E20, tracking petrol in Bharometer is, by definition, tracking your E20 mileage. There is no separate fuel type to select; the data you enter is already E20 data. ## The Practical Approach Over the Next Three Months Start your log at the next fill-up. Fill the tank to brim, note the odometer, and log it. Do the same at every subsequent fill-up without exception. After four fill-ups, calculate your average mileage. After eight, you will have a picture reliable enough to draw conclusions from. If your average is within 2% of your pre-April baseline, you are in the expected range for an E20-compatible vehicle. If it is off by 5% or more and a routine service check (tyres, air filter, plugs) does not recover it, take the log to a service centre: a printed or screenshotted mileage history with dates, fill volumes, and km/l figures is a far more useful document than "it feels worse since the petrol changed." The fuel changed. The only question worth answering is what it changed by, specifically for your vehicle, in your city, in your conditions. A log answers that. Impressions do not. --- Bharometer is a free fuel, mileage and running-cost tracker for India (iPhone). https://bharometer.com