Some days, Valerie Thoms feels like she’s living in the arcade game “Frogger.” In the 1980s game, players guide frogs across a busy road to their homes, avoiding traffic and other hazards.
Thoms is a fuel quality inspector with the NCDA&CS Fuel Quality Program. Watching closely for moving vehicles, she safely maneuvers her way from pump to pump, gathering samples of fuel. She’ll take the samples back to her mobile laboratory and conduct fuel quality tests while still at the retail location. If she finds a problem, she’ll order the station to stop the sale of the product until it can be remedied.
Whether gas prices are high or low, inspectors with the NCDA&CS Fuel Quality Program are inspecting gas stations each day to ensure the gas you’re paying for is a quality product.
“We’re here to make sure people get a good quality product when they’re coming to the gas pump,” Thoms said. “Regardless of what price they have to pay that week, we’re making sure they’re always getting a safe, quality product.”
Field inspectors across the state conduct unannounced, routine inspections at gas stations in their coverage areas to check the labeling of the products, the quality of the fuel from the gas pump and the quality of the fuel in the storage tanks.
First, they check the labels on fuel pumps to verify the product that the consumer is purchasing is clearly identified and that any additional labeling is present when applicable.
As they are checking those labels, inspectors are also gathering small samples of fuel from several of the pumps at the station. Inspectors collect samples of the station’s regular, mid-grade, premium and diesel fuel to be tested.
Then they take those samples to their mobile laboratory for testing. Regular, mid-grade and premium gasoline are tested for octane, distillation, ethanol, water and sediment, and phase separation.
The octane number is a measure of the gasoline’s ability to withstand autoignition. In the field, inspectors use a portable octane screener that uses infrared light to analyze fuel samples. Some engines might require higher-octane gas, so this test confirms the gas being sold as “premium” or “plus” meets those specifications.
Testing the fuel’s distillation end point allows inspectors to determine whether the fuel has been contaminated with diesel or kerosene, which can damage an engine. By law, the percent ethanol by volume must be displayed on the dispenser and is limited to specific volume ranges based on engine types. Inspectors in the field test gasoline products to verify these fuels meet the required specifications.
Diesel, biodiesel blends and kerosene are also tested for flashpoint – which would indicate whether the fuel is safe to use or if it has been contaminated with a fuel that has a lower boiling point, such as gasoline.
Samples are also routinely tested at the central laboratory in Raleigh. If a test in the field or at the lab finds a problem with the fuel quality, a Notice of Violation is issued and the retailer must stop the sale of the product.
Fuel quality inspectors also test for the presence of water and sediment and phase separation in the fuel samples from the dispenser as well as the fuel sitting in storage tanks. If fuel is contaminated with water, it can result in poor engine performance and possible failure. Sediment in fuel can clog fuel lines and reduce engine performance.
Excess water in gasoline causes phase separation, which is when the ethanol attaches to the water molecules and sinks to the bottom of the tank. This ethanol and water mixture is caustic and can lead to engine damage. If water or phase separation is detected in a storage tank during a routine inspection, the retailer is issued a Notice of Violation and ordered to stop the sale of that product immediately.
When the station has had remediation work done for the product, an inspector reinspects the product. Once it meets specifications, the station can resume sales of that product.
The Fuel Quality Program is made up of 11 field inspectors who are stations across the state in designated territories consisting of several counties each. Typically, gas stations are inspected at least once a year.
Inspectors also conduct complaint investigations when suspected poor fuel quality is reported by consumers. In 2025, 300 complaints were filed and 63 of them were found to have fuel quality violations. If you think you’ve purchased bad gas, you can file a complaint by calling the laboratory at (984) 236-4770 or online at www.ncmhtd.com/NCDACS/Standards/FuelComplaint.
While NCDA&CS doesn’t control the price you pay at the pump, inspectors work daily to ensure the product you’re paying for is safe for your car, boat or lawn mower.