Class Action Claims Companies Recklessly Sold Colorado Drivers Unleaded Gas Contaminated with Diesel Fuel

New to ClassAction.org? Read our Newswire Disclaimer

A proposed class action lawsuit claims that several major distributors recklessly delivered to dozens of Colorado gas stations more than 400,000 gallons of unleaded gasoline contaminated with diesel fuel, causing substantial vehicle damage for thousands of drivers.

Want to stay in the loop on class action lawsuits that matter to you? Sign up for ClassAction.org’s free weekly newsletter.

According to the 21-page complaint, Dillion Companies, LLC, which does business as King Soopers and City Market, and HF Sinclair Corporation delivered hundreds of thousands of unleaded regular- and plus-grade gasoline to dozens of gas stations throughout Colorado on January 7, 2026. Per the suit, the gas originated from a third-party supplier in Henderson, Colorado, and was shipped to a number of branches of varying retailers, including Sinclair, Circle K, Safeway, Costco, and Murphy Express.

However, the class action lawsuit alleges that, due to oversight in quality control and inspection, the retailers, unbeknownst to them, received unleaded gasoline that had been mixed with diesel fuel. The filing stresses that vehicles that run on unleaded gas can be damaged catastrophically should that fuel be mixed with diesel.

“Gas-powered vehicles are not designed to operate using diesel fuel or fuel contaminated with diesel,” the case emphasizes. “Even small amounts of diesel mixed into unleaded gasoline can cause immediate drivability issues, injector fouling, fuel system damage, and catastrophic engine failure.”

Related Reading: Murphy Premium Gas Mixed With Some Lower-Grade Fuel, Class Action Says

As a result of the widespread contamination, the complaint says, thousands of drivers in Colorado who pumped what they thought was unleaded regular- or plus-grade gasoline into their vehicles after January 7 experienced “immediate or near-immediate” engine problems after their cars started running. By the afternoon of January 9, the lawsuit says, over 200 complaints— a figure that would eventually triple in less than a week’s time— had been filed with the Colorado Division of Oil and Public Safety (DOPS) by drivers experiencing engine problems “consistent with contaminated fuel.”

“Many of the affected vehicles required towing (and associated economic costs) to auto repair facilities or dealerships because they had become unsafe or inoperable,” the case details. “For multiple vehicles, auto repair facilities conducted diagnostic testing of fuel drawn from their vehicles and confirmed the presence of diesel in the fuel systems.”

In response, the Colorado DOPS initiated fuel testing at a number of gas stations throughout the state and, by January 11, had notified approximately 3,000 gas station owners of the contamination risk.

The lawsuit contends that the gas distributor defendants “owed a duty” to the public to ensure, through thorough testing and monitoring procedures, that their gas was safe and functional before it was made available to drivers.

At minimum, if diesel exposure occurred, the entire gas tank of the afflicted vehicle must be drained and flushed, which can cost hundreds of dollars, the case notes.

“If the gasoline vehicle was driven with diesel in the gas tank, as was the case for most of the Class, other repairs are often needed, including, without limitation: replacing the spark plugs, serving [sic] the fuel injectors and filters, and sometimes even completely replacing the engine,” the complaint states. “These repairs are substantial and can cost several thousand dollars or more.”

The plaintiff, a Colorado resident, filled the tank of her Subaru Outback with what she believed was unleaded plus-grade gasoline from a King Sooper’s station on the morning of January 8, 2026. When attempting to start her car shortly thereafter, the engine struggled to start, forcing her to send her car in for repairs and obtain a rental, the filing shares.

“Defendants failed to disclose to Plaintiff and Class members and/or actively concealed from them that the motor fuel was and is defective, amounting to a deceptive trade practice under the Colorado Consumer Protection Act,” the suit alleges.

The Colorado diesel contamination class action lawsuit seeks to represent all consumers who purchased unleaded regular- or plus-grade gasoline that originated from the HF Sinclair Corporation’s Henderson Terminal and was contaminated with diesel fuel.

Additionally, the lawsuit outlines a subclass of consumers who purchased contaminated unleaded regular- or plus-grade gasoline originating from the Sinclair terminal at a gas station owned and operated by King Soopers.

Check out ClassAction.org’s lawsuit list for current class action lawsuits.