Colorado Gas Station Blunder: Diesel Fuel Sold Instead of Unleaded (2026)

Oops! Imagine pulling up to the pump, expecting regular unleaded, and unknowingly filling your car with diesel. That's precisely what happened to unsuspecting drivers in Colorado recently, sparking a flurry of concern and prompting swift action.

This article is based on firsthand information gathered by reporters, including direct interviews with sources and analysis of primary source documents.

State officials issued a warning after numerous customers reported receiving diesel fuel instead of regular unleaded gasoline at various gas stations, including Costco, King Soopers, and Murphy Express. The mix-up occurred on Thursday, and the state’s Division of Oil and Public Safety immediately launched an investigation.

The issue stemmed from a Sinclair terminal in Henderson, which mistakenly loaded diesel fuel and sent it to several gas stations between 2 p.m. Wednesday and 6 a.m. Thursday. A sample taken from a Costco gas station in Sheridan confirmed the contamination. The state agency is actively testing fuel to identify all affected retailers, and station owners are working to halt the sale of the incorrect fuel.

While the Division did not provide a complete list of impacted gas stations, a representative from King Soopers confirmed that about a dozen of their stations received the wrong fuel. They took "immediate action" by shutting down fuel lines and conducting diagnostic tests.

Here's a list of the King Soopers gas stations affected:

  • 14967 Candelas Pkwy., Arvada
  • 25701 E. Smoky Hill Rd., Aurora
  • 17000 E. Iliff Ave., Aurora
  • 3050 S. Peoria St., Aurora
  • 1045 S. 1st St., Bennett
  • 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
  • 1611 Pace St., Longmont
  • 12959 S. Parker Rd., Parker
  • 17761 Cottonwood Dr., Parker

Representatives from Costco and Murphy Express did not immediately provide a list of their affected stations.

But here's where it gets controversial... the impact on your car's engine depends on how much diesel fuel ended up in your tank. According to Stephen Martindale, service director at Phil Long in Denver, if your tank was nearly empty and you filled up with diesel, your car might only run for a short distance before stalling. This is because gasoline engines cannot generate enough heat to ignite diesel fuel.

If you suspect you've been a victim of this fuel mix-up, Martindale recommends taking your car to a dealership. Mechanics will likely drain the tank, flush the fuel lines, replace the fuel filter if necessary, and add a fuel additive to clean things up.

And this is the part most people miss... The estimated cost for these repairs could be around $1,000, including the disposal of the contaminated fuel. The final price tag depends on how much fuel needs to be drained.

"It’s contaminated, it’s no good to anybody," Martindale stated.

If you believe you received contaminated gas, you can file a complaint with the Division online or by calling 303-866-4967.

What are your thoughts on this situation? Have you ever experienced a similar issue? Share your experiences and opinions in the comments below!

Colorado Gas Station Blunder: Diesel Fuel Sold Instead of Unleaded (2026)

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