On March 6th, 2026, state officials fined Sinclair more than $365,000 after employees at the fuel distribution site had left a valve open and mixed diesel with regular unleaded gas, according to a new report released Friday.

The investigation found the mistake by workers at the Sinclair terminal in Henderson on January 7th led to the contamination of more than 1.6 million gallons of gasoline, which was sold to nearly 50 gas stations across the Front Range.

The state received about 1,909 complaints from drivers who said that their cars began to stall or sputter shortly after filling up their tanks or saw that their engine lights had turned on. They started receiving these complaints on Thursday after the dismal fuel was loaded from the Sinclair terminal. This was sent to many gas stations in the Denver metro area between 2 P.M. Wednesday and 6 A.M. on Thursday.

The division fined Sinclair $365,964 for the contamination—$1 for each gallon of contaminated fuel. The oil company has implemented a verification system that requires two people to use a certain checklist and verify the opening and closing of valves.

The diesel fuel with the unleaded regular gasoline began on January 7th at about 2 P.M. and was distributed to 49 other gas stations, including those at King Soopers, Costco, and Murphy Express. Before the employees discovered the issue at 6 A.M. the following day, according to the stations.

The fuel carriers reported the issue to Sinclair, but at that point the contaminated fuel had already been sold to gas stations, the report said.

On January 8th, Sinclair began to notify fuel carriers but did not tell the state’s Division of Oil and Public Safety. Complaints flooded into the state that morning, and state investigators confirmed that the sale had contaminated fuel at the Costco station in Sheridan. The state employees continued to test the fuel to identify the impacted retailers, and station owners were working to stop the sale of the bad fuel.

Those who were affected by the contaminated gas saw up to thousands of dollars in repair costs as mechanics had to flush tanks, clean fuel injectors, and check spark plugs, is what the auto repair professionals have said.

The division believed the bad fuel was isolated to one gas station, but as more and more complaints came in, officials realized that this was more of a widespread issue. The investigators proceeded to take gas samples from several gas stations and traced that the source of the fuel led to the Henderson terminal.

The following day, January 9th, the state asked Sinclair to provide a list of all the affected gas stations so it could inform the impacted customers. However, the oil company didn’t provide the list until January 13.

The equipment that was designed to monitor tanks also alerted operators that there was a certain problem with the fuel quality shortly after the deliveries were made. When the owners heard about that. They acted quickly to stop the sales after they were notified by Sinclair of the contamination.