The Centre questioned Karnataka’s ethanol testing process after the state claimed petrol contained 26-31 percent ethanol. The Ministry of Petroleum and OMCs said the sampling and laboratory methods used in the October 2026 exercise were wrong. They noted that rules require specific procedures to ensure dealers can verify all findings.
These procedures have come under scrutiny following Karnataka's Congress government claiming that petrol sold at certain retail outlets in the state contained 26-31 percent ethanol, significantly above the prescribed E20 limit of 20 percent ethanol.
The Ministry of Petroleum and Natural Gas (MoPNG) and the three public sector OMCs -- Indian Oil Corporation Limited (IOCL), Bharat Petroleum Corporation Limited (BPCL) and Hindustan Petroleum Corporation Limited (HPCL) -- have questioned both the sampling process and the laboratory methods used in Karnataka's October 2026 exercise.
The latest controversy comes amid wider concerns over E20 petrol. In July, the policy faced criticism over possible mileage losses, particularly in older vehicles. The Society of Indian Automobile Manufacturers (SIAM) also flagged fuel-quality concerns, including chloride contamination and moisture, in a communication to the petroleum ministry. It later withdrew the communication, saying some figures needed further authentication.
While the July debate centred on mileage and vehicle compatibility, the Karnataka controversy concerns whether petrol contained more ethanol than permitted. The process requires petrol samples to be collected and analysed in accordance with prescribed procedures.
According to Centre, these procedures are laid down under the Motor Spirit and High-Speed Diesel (Regulation of Supply, Distribution and Prevention of Malpractices) Order, 2005, issued under the Essential Commodities Act, 1955, and the Marketing Discipline Guidelines (MDG) 2024.
Under these rules, six one-litre samples must be collected from a petrol outlet. Two are handed to the dealer against acknowledgement, two are retained by the oil company or inspecting department, and the remaining two are sent to a laboratory specified under the control order.
Sample labels must be jointly signed, and test results communicated to the dealer and oil company within the prescribed timeframe. This allows all parties to verify the findings and seek retesting if they disagree.
The OMCs have also questioned the use of certificates from a third-party laboratory instead of a laboratory specified under the control order. The OMCs say the absence of samples and documentation has prevented them and the dealers from independently verifying the results or seeking a retest.
What methods should laboratories use?
Even if samples are collected correctly, laboratories must follow prescribed technical standards to establish their ethanol content.
The relevant specification is identified under IS 17021:2018, the Bureau of Indian Standards (BIS) standard for ethanol-blended motor gasoline. The amendment, issued in August 2025, prescribes three methods for measuring ethanol content in E20 petrol.
The first is Fourier Transform Infrared Spectroscopy (FTIR), which uses infrared light to identify and measure the concentration of substances in a fuel sample.
The second is water extraction method. Since ethanol mixes readily with water while petrol does not, this method uses water to separate ethanol from petrol before measuring its content through the prescribed procedure.
The third is Gas Chromatography, a laboratory technique that separates the different chemical components of a fuel sample so their individual quantities can be measured. It must follow the prescribed ASTM D4815 or D6839 standards. ASTM International is an organisation that develops standardised testing methods for materials and products.
Gas Chromatography also has specific requirements. The sample must first be diluted in equal proportions with oxygenate-free petrol, meaning petrol without ethanol or other oxygen-containing blending components. The result must then be corrected using an E10 certified reference material -- a sample with a known composition used to check the accuracy of laboratory measurements.
The Centre says Karnataka's laboratory certificates only mention that ethanol was measured using Gas Chromatography. They do not specify which ASTM standard was followed, whether the required dilution was carried out or which reference material was used.
Without these details, the reported ethanol levels of 26-31 percent cannot be independently validated against IS 17021, the Centre argues.
Why the Centre questioned the results
The Ministry has questioned the density readings in Karnataka's certificates. Since ethanol is denser than petrol, a higher ethanol proportion would ordinarily be expected to increase the fuel's overall density.
Karnataka's certificates recorded densities of 0.742-0.749 grams per cubic centimetre for samples reportedly containing 26-31 percent ethanol. In comparison, OMC tests of E20 samples recorded densities of 0.752-0.760 grams per cubic centimetre. The Centre says this difference warrants further examination through prescribed testing and comparison with appropriate reference samples.
The OMCs have also cited their nationwide quality-monitoring exercise conducted with the Centre for High Technology (CHT), under Petroleum Ministry. Of 893 samples collected from depots and retail outlets across 27 states and Union Territories, all were found to contain ethanol within the prescribed range of 19-21 percent.
This included 56 samples from Karnataka, covering all three OMCs and different locations. Their ethanol content ranged between 19 and 20 percent, averaging 19.30 percent.
The OMCs have sought Karnataka's sampling records, laboratory reports and access to the samples. They have proposed joint testing at an authorised laboratory with representatives of both sides to establish whether the reported ethanol levels are accurate and meet the prescribed testing standards.