On the 29th of last month at around 3 p.m. at a gas station in Gungnae-dong, Bundang-gu, Seongnam-si, Gyeonggi Province. Director Yeon Je-won of the Korea Oil Quality Management Authority's Inspection Division filled a black sport utility vehicle (SUV) with 30,000 won worth of diesel.
The price of diesel at the gas station was 1,496 won per liter. When the notification indicated that 20.054 liters had been dispensed, the computer installed in the back seat of the vehicle displayed the number '16.46㎏'. This was the result of a scale installed in the trunk of the 'undercover inspection' vehicle operated by the Korea Oil Quality Management Authority measuring the weight of the diesel.
The Korea Oil Quality Management Authority conducts 'quality inspections' to check for fake diesel and gasoline, and 'quantity inspections' to ensure accurate dispensing. The authority operates seven undercover inspection vehicles for quality checks and 16 for quantity checks. Vice Administrator Kim Kyung-ho and Director Yeon joined the undercover inspection vehicle from the authority's head office located in Bundang-gu, Seongnam-si, Gyeonggi Province.
The diesel or gasoline dispensed into the undercover inspection vehicle is transferred to a temporary storage tank equipped with a scale in the trunk after inspection. Although a divider is installed between the backseat and trunk, the inside of the inspection vehicle was filled with the smell of fuel immediately after the refueling.
Typically, inspectors move to another location after refueling to complete the rest of the inspection. When Director Yeon pressed the 'sample collection' button installed in the trunk, a light yellow diesel collected in the temporary storage tank rose through a transparent tube and was contained in a small container. When a portable density meter was placed inside, the number 0.817 appeared. The normal diesel density ranges from 0.815 to 0.835, so the diesel fueled that day passed the quality standard.
Next, the quantity is confirmed. After entering the density measured with the portable density meter into the computer, the laptop displayed '100.46 (appropriate)'. If it had been marked as inappropriate, a face-to-face inspection would be conducted, revealing the identity of the inspector from the Korea Oil Quality Management Authority.
The Korea Oil Quality Management Authority operates undercover inspection vehicles because some individuals mix kerosene with diesel for sale. Kerosene is commonly used as a home boiler fuel, which incurs lower taxes than diesel, enabling unfair profit. According to the Petroleum and Alternative Fuel Business Act, anyone who sells fake diesel may face business suspension, penalty surcharges, or criminal punishment. Users can also be subject to fines of up to 30 million won.
The Korea Oil Quality Management Authority also conducts undercover operations to eradicate the distribution of fake diesel. Fake diesel is mainly distributed through mobile sales. Mobile sales refer to the delivery and sale of diesel or kerosene outside gas stations using small tank trucks, commonly referred to in the refining industry as 'home lorries.'
Household boilers and construction machines such as excavators and cranes can be refueled on the go. However, dump trucks and ready-mix concrete trucks, while categorized as construction machinery, must be refueled at gas stations like regular passenger cars or trucks since they are registered vehicles that operate on roads.
Fueling dump trucks or ready-mix concrete trucks through mobile sales is illegal, and fake diesel may be detected in the process. Director Yeon noted, 'Kerosene contains a dye marker, and when a color agent is added, fake diesel containing kerosene turns purple.'
Undercover operations mostly rely on reports. When a report is received indicating that mobile sales of fake diesel are taking place at specific locations, they collaborate with the police to conduct undercover operations. To this end, the Korea Oil Quality Management Authority operates a reward system for reports. Director Yeon remarked, 'If fake diesel or substandard quantity is detected through a report, the informant will receive a reward.'
The number of cases of fake diesel detection has decreased from 83 in 2021 to 59 in 2022, 48 in 2023, and 21 in 2024. Vice Administrator Kim stated, 'Fake diesel can always be distributed systematically, so we cannot let our guard down.'