What Should You Do Immediately After Putting Gasoline in a Diesel Vehicle?
So, you’re standing at the pump, keys in hand, and it hits you—you just filled your diesel car with gasoline. Your stomach drops. First things first: don’t panic. You’re not the first, and you won’t be the last. But quick action is crucial to prevent serious (and expensive) damage.
The most important step? Don’t start the engine. If you haven’t turned the key yet, you’re in luck. Starting the engine circulates gasoline through the fuel system, which can wreak havoc on diesel components. Diesel engines rely on the lubricating properties of diesel fuel, and gasoline is a poor substitute. Without that lubrication, fuel pumps and injectors can seize or wear out rapidly.
If you’ve already started the engine, turn it off immediately. The less gasoline that moves through the system, the better your chances of minimizing damage.
Why Is Mixing Gasoline With Diesel So Bad?
You might wonder, isn’t fuel just fuel? Not quite. Diesel engines are built for a thicker, oilier fuel that burns differently than gasoline. Gasoline is more volatile and lacks the lubricating qualities diesel engines need. When gasoline enters a diesel system, it can cause metal parts to grind against each other, leading to costly repairs—sometimes even a full engine replacement.
According to the American Automobile Association (AAA), misfuelling incidents are surprisingly common, especially with rental vehicles or when switching between gas and diesel cars. In 2022, AAA reported assisting over 150,000 drivers nationwide with fuel-related mishaps, many involving the wrong fuel type.
How Much Gasoline Is Too Much in a Diesel Tank?
A tiny splash of gasoline—say, less than 5% of the tank—might not spell disaster, especially if you catch it before starting the engine. But anything more than that, and you’re rolling the dice. Even small amounts can reduce lubrication, increase wear, and create performance issues.
If you’ve filled up with more than a couple of gallons, it’s best to play it safe and get the tank drained. Some modern diesel vehicles have sensors that can detect the wrong fuel and trigger warning lights, but don’t rely on this as your safety net.
What Steps Should You Take Next?
Once you realize the mistake, here’s your action plan:
1. Don’t start the engine. If it’s already running, shut it off right away.
2. Inform the station attendant. They may have procedures for handling fuel spills or misfuelling.
3. Call roadside assistance or a trusted mechanic. Explain the situation—most professionals have seen this before and can advise on the next steps.
4. Arrange for a fuel drain. This involves removing the contaminated fuel from the tank and flushing the fuel lines. It’s not a DIY job for most people, as improper handling can be dangerous and may void warranties.
If you’re in a remote area, some tow services specialize in misfuelling incidents and can come to you. The cost varies, but it’s almost always cheaper than repairing a damaged diesel engine.
Can You Fix It Yourself?
Tempted to siphon the tank yourself? Unless you’re experienced and have the right equipment, it’s risky. Modern diesel vehicles often have anti-siphon devices, and spilled fuel is a fire hazard. Plus, you might not be able to remove all the contaminated fuel, leaving traces that could still harm your engine.
If you’re mechanically inclined and the vehicle is older, you might be able to drain the tank from underneath. But for most drivers, calling a professional is the safest bet.
What If You Drove a Short Distance Before Realizing?
If you only drove a few yards or blocks, don’t beat yourself up. Turn off the engine as soon as possible and call for help. The more gasoline that circulates, the greater the risk of damage. A mechanic will likely recommend draining the tank, replacing the fuel filter, and inspecting the fuel system for signs of wear.
In some cases, you might get away with minimal repairs, especially if you acted quickly. But if the engine ran for a while, be prepared for a more thorough inspection—and possibly a higher repair bill.
How Can You Prevent This From Happening Again?
Let’s be honest: misfuelling often happens when we’re distracted or in a hurry. Here are a few tips to avoid a repeat performance:
– Stick a “Diesel Only” label near your fuel cap.
– Always double-check the pump handle color and label before fueling.
– If you drive both gas and diesel vehicles, make a habit of confirming the fuel type every time.
– Some drivers even keep a reminder card on their dashboard.
A 2023 survey by the UK’s RAC Foundation found that clear labeling and reminders cut misfuelling incidents by nearly 40 percent. A simple sticker could save you thousands.
What Damage Can You Expect—and How Much Will It Cost?
The worst-case scenario? Major engine damage requiring a full rebuild or replacement, which can run into the thousands. More often, if you catch the mistake early, you’ll only need a tank drain and filter change, typically costing a few hundred dollars.
Insurance may cover some of the costs, especially if you have comprehensive coverage, but check your policy. Some insurers exclude misfuelling, considering it driver error.
The Big Takeaway
Putting gasoline in a diesel vehicle isn’t about perfection—it’s about smarter adjustments. Start with one change this week—maybe a bright sticker on your fuel cap or a quick double-check at the pump—and you’ll likely spot the difference by month’s end. Mistakes happen, but a fast, informed response can turn a potential disaster into just another story for the road.
