Look, it happens. You were distracted, grabbed the wrong handle, and put it in your truck without thinking about it. Every fueling station has different colored handles for the diesel pumps, but you got confused and put gasoline in your diesel-powered vehicle. How bad could it be? Gasoline and diesel are both liquids used to power engines, after all.
If you accidentally pump gasoline into your diesel engine — even a little bit — you shouldn’t even try to start it. The best course of action is to have the vehicle towed to a shop and the entire fuel system drained. There is a reason diesel and gasoline pumps use separate nozzles: even the smallest amount of gasoline held in the pump hose can completely ruin your diesel vehicle. Different grades of gasoline can share a pump handle, and mixing those together isn’t the end of the world, but diesel is a different beast.
The two fuels may seem alike, but pumping the wrong one into your car could wreck your day, if not your ride. Even with a small amount of gasoline in your diesel tank, you’ll likely notice significant performance issues. Gasoline-contaminated diesel will result in incomplete combustion, misfires, and potential damage to your fuel system components. Gasoline is particularly harsh on high-pressure diesel fuel injectors, potentially causing long-term fuel delivery issues even after the gasoline is removed from your tank. Incomplete combustion can also create hot spots inside the engine’s combustion chamber, potentially overheating and damaging the cylinder walls and pistons.
How Long Can You Drive With Gasoline in Your Diesel Tank?
While both fuels are derived from crude oil, the similarities largely end there. Gasoline is a more refined fuel, making it less dense and more combustible than diesel, requiring lower compression and lower temperatures to burn. Diesel, meanwhile, contains about 20% more energy per gallon and requires high compression to ignite, producing a slower burn and better thermal efficiency. Gasoline combustion in a diesel engine will also cause significant black smoke and carbon buildup, potentially leading to sticky or damaged exhaust valve seats. Gasoline can clog fuel lines and filters, and it lacks the lubricants that fuel pumps and injectors depend on.
Even if you don’t notice any issues right away, gasoline will adversely affect your engine’s performance and fuel economy. At the very least, the engine will run rougher, respond sluggishly, smoke significantly, and make abnormal knocking or clattering sounds. Gasoline will also cause a diesel engine to stall randomly, if it even starts at all.
These are not trivial damages. At best, your engine runs a little rough — potentially forever. At worst, you need to get your engine rebuilt or replaced. Putting any amount of gasoline in a diesel engine is taking a significant risk. Even with a diesel-powered vehicle like a 2013 Porsche Cayenne, running it with even a thimble of gasoline in the fuel tank isn’t worth considering.
I Only Put a Little Bit In — How Much Damage Could It Do?
You may have heard stories from friends who got away with a bit of gasoline in their diesel tanks. And the fact is, you might escape damage if you catch yourself early enough. Say you got about half a gallon in before stopping — there’s a chance you could get off scot-free, but there’s also a real likelihood your vehicle will need thousands of dollars in repair work as a result. Yes, it’s annoying to have your car towed and completely drained, and fuel isn’t cheap. But consider the alternative.
Even with a costly fill-up wasted, you’re still several thousand dollars short of where you might end up if you need a full fuel system rebuild or a new engine. It simply isn’t worth the risk to try to burn through the gasoline in your tank. Gasoline won’t separate into layers within diesel — it fully integrates, meaning all of the diesel in your tank is now contaminated and no longer usable. The right move is to bite the bullet, get the tank drained, flush the fuel lines, and refill with fresh diesel. If you try to push through and ignore the problem, things will only get worse.
