Around midweek, dozens of Colorado drivers found themselves stalled on the side of the road with sputtering engines and a sinking feeling: the gas they'd just bought wasn't gasoline.
State inspectors say late Wednesday into early Thursday deliveries of contaminated fuel — diesel in regular unleaded tanks — were pumped into cars and trucks at multiple retail stations across the Denver metro area and beyond. The result: engines that lurched to a stop, expensive repairs and a fast-moving consumer complaint investigation.
What happened
Colorado’s Division of Oil and Public Safety started getting complaints when drivers reported their vehicles dying shortly after filling up. An on-site inspection at a Costco station in Sheridan produced a sample that tested positive for diesel in a regular-gasoline holding tank, the agency said.
Officials now believe the affected loads originated from a Sinclair terminal that serves many outlets in the state. The agency says deliveries in question took place between about 2 p.m. Wednesday and 6 a.m. Thursday — a window drivers should keep in mind when checking receipts.
Retailers named in reports include King Soopers, Costco and Murphy Express. King Soopers confirmed contaminated unleaded fuel was delivered by a third-party carrier to nearly 20 of its Denver-metro gas stations and said it shut down affected lines as soon as it learned of the problem and dispatched teams to remediate tanks and pumps.
Here are the King Soopers locations the chain identified as affected (company list):
- 14967 Candelas Pkwy., Arvada
- 25701 E Smoky Hill Rd., Aurora
- 15109 E Colfax Ave., Aurora
- 17000 E Iliff Ave., Aurora
- 3050 S Peoria St., Aurora
- 19001 E Quincy Ave., Aurora
- 1045 S 1St St., Bennett
- 3600 Table Mesa Dr., Boulder
- 1650 30Th St., Boulder
- 12167 Sheridan Blvd., Broomfield
- 2355 W 136Th Ave., Broomfield
- 7284 Lagae Rd., Castle Pines
- 750 N Ridge Rd., Castle Rock
- 5125 W Florida Ave., Denver
- 11747 W Ken Caryl Ave., Littleton
- 9820 W Belleview Ave., Littleton
- 1611 Pace St., Longmont
- 12959 S Parker Rd., Parker
- 17761 Cottonwood Dr., Parker
- Stop driving the vehicle if it is behaving oddly. Continued operation can do further damage.
- Keep your pump receipt and note the time you filled up.
- Photograph the pump, price label, and any warning or taped-off pumps.
- Contact the station where you purchased fuel and ask about their claims process.
- File a complaint with Colorado’s Division of Oil and Public Safety so regulators can trace the load.
- Get a mechanic’s inspection and a written estimate — you'll need documentation for claims or insurance.
King Soopers later removed a few locations from the list after diagnostics showed those tanks were clean.
Drivers and damages
Personal stories give the scope a human face. One driver reported filling up early Thursday and making it only about four miles before her car began lurching and finally stalled. Mechanics told her diesel had been mixed into her gas tank; initial repair estimates ran from roughly $1,300 to as much as $5,000 for others.
If diesel is introduced into a gasoline vehicle, fuel-system components can be fouled, injectors damaged and catalytic converters stressed — repairs that add up quickly. That’s why affected drivers are already weighing whether to pursue retailer claims or go through their own insurance.
Who’s investigating and what you should do
The Division of Oil and Public Safety is the lead for consumer complaints and is collecting reports to trace where contaminated loads went. Trade groups and Sinclair have reportedly been in touch with the state and local marketers about mitigation.
If you filled up during the suspect window and think you may be affected, the practical steps are straightforward and time-sensitive:
Retailers have urged customers who believe they were impacted to contact stores directly so claims can be handled. The situation has prompted some drivers to consider using their insurers if claims handling feels slow or incomplete.
Why this matters beyond immediate repairs
Fuel supply chains are complex: terminals, third‑party carriers, local storage tanks and pumps all have to line up perfectly. When one piece breaks down — whether human error, a cross-fill at a terminal, or contaminated batches — effects ripple fast across multiple stations serviced by the same source. That’s why the state is focused on tracing loads from terminals to individual outlets.
Car repairs after fuel contamination can be unexpectedly large, especially on modern engines with sensitive fuel-injection systems — a reminder that what seems like a routine fill-up can become an expensive problem. For drivers who treasure their vehicles or own modified cars, the stakes are even higher; aftermarket or high-performance components can complicate diagnostics and repairs, as seen in discussions around recent SEMA and performance-vehicle coverage like the Ford Maverick turbo kit story and deep dives into high-output muscle cars such as the Dodge Sixpack Charger.
Officials and retailers say remediation is underway and pumps will return to service only after diagnostics confirm tanks and lines are clean. For now, if you pumped gas within the stated timeframe and your vehicle is acting up, treat it as an urgent problem: document everything, contact the station and file a complaint with state regulators so the scope of the incident can be fully mapped and resolved.