Adulterated fuel — petrol cut with kerosene or naphtha, or diesel cut with cheaper solvents — is still sold at some unbranded and rural pumps across India, though enforcement has tightened since BS6 rollout. Warning signs include a sudden 10-20% drop in mileage, engine knocking, black exhaust smoke, and a kerosene-like smell at the pump. You can request an on-the-spot filter paper test or density check at any petrol pump under Legal Metrology rules, free of cost. If you suspect adulteration, keep the receipt and file a complaint with the State Legal Metrology Department or call the oil marketing company's toll-free number printed at the pump.
At a glance
| Check | What it tells you |
|---|---|
| Filter paper test | Free at every pump; spreading kerosene-cut fuel leaves a translucent stain that doesn't evaporate clean |
| Density meter reading | Petrol: 720-775 kg/m³, Diesel: 830-900 kg/m³ at 15°C — printed on the pump display |
| Mileage drop | A sudden 10-20% fall with no driving-pattern change is the most common early sign |
| Where it's more common | Unbranded pumps on highways and rural stretches, far less common at branded outlets in metros |
| Your right to test | Every consumer can demand a free density/filter test under the Legal Metrology (Packaged Commodities) framework |
How fuel adulteration actually works
Adulteration means diluting petrol or diesel with a cheaper liquid — kerosene, naphtha, or industrial solvents — to pocket the price difference. Kerosene is subsidised and far cheaper than petrol, which is exactly why it has historically been the adulterant of choice in parts of India. The practice is illegal under the Essential Commodities Act and Motor Spirit and High Speed Diesel (Regulation of Supply, Distribution and Prevention of Malpractices) Order, but it hasn't disappeared — it has simply moved to smaller, unbranded outlets where enforcement visits are less frequent.
Since BS6 emission norms and stricter Oil Marketing Company (OMC) audits came into force, adulteration at branded pumps (Indian Oil, Bharat Petroleum, Hindustan Petroleum, Shell, Nayara) is rare. Risk is concentrated at standalone rural pumps and along interstate highway stretches with weak local oversight.
Warning signs while driving
- Sudden mileage drop of 10-20% with no change in traffic, load or driving style
- Engine knocking or pinging, especially under load or while overtaking
- Black or unusually heavy exhaust smoke, particularly on start-up
- Rough idling or hesitant acceleration that wasn't there before
- A kerosene-like smell at the pump nozzle or in the exhaust
- Difficulty starting the car in the morning after refuelling at a new station
How to test fuel on the spot
Every petrol pump in India is legally required to let you test fuel quality free of charge. Ask the attendant for:
- Filter paper test — a few drops of fuel are spread on a filter paper strip; pure petrol evaporates leaving no oily ring, while kerosene-cut fuel leaves a translucent, oily stain
- Density check — every pump has a hydrometer and thermometer kit; density should read 720-775 kg/m³ for petrol and 830-900 kg/m³ for diesel at 15°C, and the reading should be displayed on a board near the dispensing unit
- 5-litre test measure — you can ask for fuel to be dispensed into a calibrated 5-litre jar first to confirm both quantity and appearance before it goes into your tank
Refusal to test, a missing density chart, or an attendant who discourages you from checking is itself a red flag — walk away and refuel elsewhere. Don't rely on smell alone; some adulterants are odourless.
What to do if you suspect adulterated fuel
- Stop refuelling immediately and keep the receipt with the pump's name, date and time
- Ask for the density test result in writing if possible
- Call the toll-free customer care number printed on the pump signage (IOC, BPCL and HPCL all run 24x7 helplines)
- File a complaint with your State's Legal Metrology / Weights and Measures department, which is empowered to inspect and seal pumps
- If your car develops symptoms, get the fuel filter and injectors inspected at a workshop — adulterated fuel often clogs filters and damages fuel pumps over a few thousand kilometres
Long-term protection habits
- Stick to branded pumps on long highway drives, even if it costs a rupee or two more per litre
- Avoid topping up at unfamiliar rural pumps when your tank is already comfortably full
- Track your mileage every few fill-ups using a simple notebook or app so a sudden drop is easy to spot
- Use a genuine, undamaged fuel cap and check it hasn't been tampered with if the car was parked unattended for long
Frequently asked questions
Is fuel testing at petrol pumps really free in India?
Does adulterated fuel damage the engine permanently?
Which is more commonly adulterated, petrol or diesel?
How do I know if a petrol pump is trustworthy?
Can adulterated fuel void my car's warranty?
Sources & further reading
- Ministry of Petroleum & Natural Gas — Fuel Quality Control
- Legal Metrology Division, Dept. of Consumer Affairs
- Indian Oil Corporation — Customer Care
Figures, prices and policy details were current at the last-updated date above. Automotive pricing, incentives and regulations change frequently — verify time-sensitive details with the linked primary sources. Read our editorial policy and fact-checking standards.
