Explained: What is the ethanol issue in Karnataka and why have OMCs rejected the state govt's excess blending claims?

E20 petrol is a blend containing up to 20% ethanol and the remainder petrol. The number “20” refers to the ethanol percentage in the fuel blend, generally measured by volume. This limit matters because fuel standards define how the blend should be produced, tested and used.

The oil companies said their E20 petrol complies with BIS specification IS 17021. Karnataka, however, reported ethanol concentrations between 26% and 31% in some samples. One IOCL sample reportedly reached 31.2%, well above the stated E20 limit.

The disagreement is not only about the percentage. The OMCs also challenged how the samples were collected and tested. They said valid gas-chromatography testing requires specific procedures, including dilution and correction against a certified reference material. The companies reported that 893 samples from 27 states and Union territories, including 56 from Karnataka, stayed within 19-21%.

Karnataka said testing found ethanol above the prescribed 20% limit in petrol sold at some outlets. The state reported that 11 of 14 samples exceeded the threshold. This mattered because the fuel was supplied as E20, whose stated ethanol level is 20%.

The highest reported result was 31.2% in a sample from an IOCL outlet. An HPCL Power sample contained 30.5%, another HPCL sample contained 27%, and a BPCL Speed sample contained 26.5%. Samples came from seven districts, including Bengaluru, Kolar and Mangaluru.

The OMCs rejected the findings as procedurally unsupported. They said a separate quality-monitoring exercise tested 893 E20 samples from depots and outlets across 27 states and Union territories. All were between 19% and 21%. The companies said 56 Karnataka samples ranged from 19% to 20%, averaging 19.30%.

Karnataka reported ethanol concentrations ranging from 26% to 31% in the disputed petrol samples. These results were materially higher than the 20% level associated with E20 fuel. The state said its testing covered samples from seven districts and 14 total samples.

The most extreme result was 31.2% from an IOCL outlet. An HPCL Power sample recorded 30.5%, another HPCL sample recorded 27%, and a BPCL Speed sample recorded 26.5%. According to the state government statement, 11 of the 14 tested samples were above 20%.

The OMCs did not accept these figures as independently established. They questioned the collection process, said they had not received retention samples or full laboratory reports, and challenged the technical details in the certificates. Their own exercise reported 56 Karnataka samples between 19% and 20%, with a 19.30% average.

Independent verification requires a controlled chain from collection to testing. The OMCs said Karnataka’s October 2026 samples were collected without OMC representatives. They also said they did not receive counterpart retention samples, complete outlet-wise information or the laboratory reports they requested.

The companies pointed to the prescribed procedure under the 2005 Control Order and MDG 2024. Six one-litre samples should be collected. Two go to the dealer, two are retained, and two go to a specified laboratory. Labels should be jointly signed, and results should reach the dealer and oil company within the required period.

They also challenged the gas-chromatography certificates. Under IS 17021, they said, testing requires 1:1 dilution with oxygenate-free petrol and correction against an E10 certified reference material. The certificates reportedly gave ethanol percentages but did not identify the standard, dilution process or reference material.

A vehicle designed for a lower ethanol blend may not handle a higher concentration as efficiently. Ethanol contains less energy per unit volume than petrol, so higher ethanol content can reduce fuel economy. The effect depends on the vehicle, engine calibration and actual blend.

Higher-than-designed blends can also affect starting, acceleration and smooth running, especially if the fuel system is not calibrated for them. Ethanol can attract water and may be harder on some older seals, hoses or fuel-system materials. In unsuitable vehicles, repeated use could increase maintenance or repair costs.

The article does not say that Karnataka’s disputed samples caused mileage loss, performance problems or repairs. It focuses on whether the samples were collected and tested correctly. It reports that more than 30 crore two-wheelers and 4 crore four-wheelers have used E20 for over three years, but it gives no related cost or damage data.

OMC means oil marketing company. In this article, the term refers to Indian Oil Corporation Ltd, Bharat Petroleum Corporation Ltd and Hindustan Petroleum Corporation Ltd. All three are state-run companies involved in supplying and selling petrol through their networks.

Their responsibility follows from their position in the fuel chain. The companies said blending at their refineries and depots uses calibrated, controlled systems with automatic proportioning. They also said E20 petrol supplied across the country complies with BIS specification IS 17021. Their outlets were among those sampled by Karnataka.

The companies therefore rejected the allegation that their petrol exceeded the permitted ethanol level. They said their own monitoring found all 893 tested samples within 19-21%, including 56 Karnataka samples averaging 19.30%. They also disputed Karnataka’s sampling and testing process, so the final disagreement concerns both fuel quality and evidence quality.

Ethanol blending reduces the amount of petroleum in each litre of fuel and can support domestic fuel supply when ethanol is produced from agricultural sources. It also contains oxygen, which can help petrol burn more completely. These are established reasons for blending, although the article itself mainly discusses compliance with E20 standards.

Changing the blend changes the fuel’s energy content and chemical behavior. Ethanol has less energy per litre than petrol, so mileage can fall slightly as ethanol content rises. Higher blends may require engine calibration and fuel-system materials designed to tolerate ethanol, especially in older vehicles.

The article reports that more than 30 crore two-wheelers and 4 crore four-wheelers have used E20 for over three years. It says the OMCs tested 893 samples and found them within 19-21%. The Karnataka dispute shows why consistent blending, sampling and testing matter as fuel use expands.