This Mistake of the Week episode looks at how diesel fuel ended up where it shouldn’t—and what that teaches us about system failures. Mark Graban reflects on why learning and prevention matter more than blame after a costly mistake.
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Most of us pull up to a gas pump on autopilot.
Card in. Grade selected. Nozzle lifted.
It’s a routine we rarely question—until something goes wrong.
In this Mistake of the Week, I reflect on a real-world systems failure that affected hundreds of drivers across the Denver metro area. Due to an upstream error at a fuel terminal, diesel fuel was mistakenly introduced into the gasoline supply and distributed to multiple stations. The result: stalled vehicles, tow trucks, and expensive repairs.
When stories like this break, there’s a familiar reflex:
- Who made the mistake?
- Who should be blamed or punished?
But that’s not the direction Colorado regulators took.
Instead, their focus was on understanding how the system failed and what could be changed to prevent the problem from happening again. That distinction matters—because learning and prevention are far more effective than punishment.
Mistake-Proofing Has Limits
Many people are familiar with a classic example of mistake-proofing: diesel nozzles are larger than gasoline nozzles, making it difficult to put diesel into a gasoline-powered car.
But that safeguard only works at the point of fueling the vehicle. It does nothing to prevent diesel from being loaded into the wrong tank upstream. Once the wrong fuel enters the system, downstream controls become irrelevant.
This is a reminder that mistake-proofing isn’t a gadget—it’s a mindset. Effective prevention requires asking where errors are most likely to occur and designing systems to catch them as early as possible.
A Leadership Lesson
This episode explores:
- Why blaming individuals misses systemic causes
- How upstream errors overwhelm downstream safeguards
- Why “be more careful” is not a strategy
- What leaders can learn from responding with curiosity instead of punishment
Mistakes like this are disruptive and costly. But they also create an opportunity—if organizations choose to learn, investigate, and improve the system rather than point fingers.
That’s the mistake of the week.
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Transcript:
This is Mistake of the Week. I’m Mark Graban.
Most of us pull up to a gas pump on autopilot. Card in. Grade selected. Nozzle lifted. It’s a routine we rarely question—until something goes wrong.
Last month, hundreds of drivers across the Denver metro area discovered that what they thought was regular unleaded gasoline… was actually diesel fuel. The mix-up originated upstream, at a Sinclair terminal in Henderson, Colorado, where diesel was mistakenly loaded and then distributed to multiple gas stations, including Costco, King Soopers, and Murphy Express locations.
The reporting comes from The Colorado Sun, with original coverage by Olivia Prentzel.
By the time regulators confirmed the issue, more than 400 motorists had reported problems—cars stalling shortly after fueling, tow trucks dispatched, and repair bills that weren’t small.
When stories like this surface, there’s a familiar instinct to look for blame.
Who made the mistake?
Who should be punished?
But that’s not the direction Colorado regulators took.
Zach Hope, petroleum program manager for the state’s Division of Oil and Public Safety, put it this way:
“The important thing is to find out how to avoid this in the future. This doesn’t benefit anybody and so Sinclair’s investigation should point to the root cause and we will work with them to make sure that they take some steps to alleviate the possibility of that happening again.”
That sentence matters.
Because it reflects a focus on learning and prevention, not blame and punishment.
Now let’s talk about mistake-proofing.
Most people know that diesel nozzles are intentionally larger than gasoline nozzles. That physical difference helps prevent a diesel nozzle from fitting into a gasoline car’s fuel tank. It’s a classic example of mistake-proofing—designing the work so an error is hard or impossible to make.
But notice the limitation.
That safeguard works only at the point of fueling a vehicle. It does nothing to prevent diesel from being loaded into the wrong underground tank at a terminal. Once the wrong fuel enters the system upstream, every downstream control becomes irrelevant.
There’s also a nuance that often gets lost. Putting unleaded gasoline into a diesel engine is actually more damaging than the reverse. But the customer mixup is error proofed only in one direction – you can’t fit the diesel nozzle into an unleaded car. But you CAN mistakenly put unleaded into a diesel car. Arguably, it’s mistake proofed in the wrong direction. But that’s a matter of history – and maybe a topic for another episode.
This is a broader lesson about mistake-proofing as a mindset, not a gadget.
The common thread isn’t telling people to “be careful.”
It’s recognizing that mistakes are predictable—and then designing systems to prevent them, catch them early, or limit their impact.
In this case, state officials have said the incident appears to be unintentional and unprecedented. They’ve also said enforcement or fines are unlikely. Instead, the emphasis is on understanding how the system failed and what needs to change so it doesn’t happen again.
That’s how progress is made.
Mistakes like this are costly and disruptive. But they also create an opportunity—if organizations choose to respond with curiosity, investigation, and better design instead of finger-pointing.
That’s the mistake of the week.
I’m Mark Graban. Thanks for listening.