can you put diesel in your car

[KalebLee]

Putting diesel fuel into a gasoline-powered car will cause significant and immediate damage to the fuel system and engine, requiring expensive repairs. Do not start the car if you realize the mistake. The fundamental issue is that gasoline and diesel engines operate on completely different principles. Gasoline engines use spark plugs to ignite a mixture of fuel and air, while diesel engines rely on compression to ignite the fuel. Diesel fuel is much oilier and acts as a lubricant for diesel engine components, but it will clog a gasoline engine's finer fuel injectors and fuel lines.

The damage begins as soon as you try to start the car. Diesel won't vaporize properly in the intake system and can't be ignited by the spark plugs. It will foul the spark plugs and flood the cylinders. If the engine does run, it will produce excessive smoke and run very poorly. The real danger is to the high-pressure fuel pump and injectors in modern direct-injection gasoline engines; these precision components are lubricated by gasoline itself, and diesel's thicker consistency can cause them to fail catastrophically due to a lack of lubrication.

Your immediate action steps are critical:

1. Do not start the engine. This is the most important rule. Simply turning the key to the "on" position without cranking the engine can still pump some diesel into the system, but starting it circulates the contaminant throughout the entire fuel system.
2. If you haven't started the car, you have the best-case scenario. The car will need to be towed to a repair shop where technicians can completely drain the fuel tank and flush the entire fuel system.
3. If you have started and driven the car, the damage is likely already done. The car still needs to be towed for a full system drain and flush, but you will also be looking at potential repairs or replacements for the fuel pump, fuel injectors, spark plugs, and possibly catalytic converter damage from the unburned fuel. The cost can easily run into thousands of dollars.

Fuel Property	Gasoline	Diesel	Consequence in a Gasoline Car
Ignition Method	Spark Ignition	Compression Ignition	Diesel will not ignite, causing misfires.
Viscosity / Lubricity	Low (solvent)	High (oily)	Clogs injectors; damages fuel pump.
Cetane vs. Octane Rating	High Octane	High Cetane	Incompatible with engine control software.
Typical Repair Cost (US)	-	-	$1,500 - $5,000+ for full system repair.
Primary Component at Risk	-	-	High-pressure fuel pump & fuel injectors.

[Gama]

Do not turn the key. Seriously. I've seen this in the shop more times than you'd think. Diesel in a gas car is bad news. It gums everything up—the fuel pump, the tiny holes in the injectors—because it's too thick. The best thing you can do is have it towed to a mechanic. If you haven't started it, you might get away with just a very expensive tank drain and system flush. If you drove it, prepare for a bill that could buy you a decent used motorcycle.

[NathanMarie]

My neighbor did this last year at a confusing pump station. His SUV started billowing white smoke and stuttered to a stop halfway home. The repair bill was over four thousand dollars. The mechanic explained that the diesel essentially starved the engine's sensitive components of lubrication. The entire fuel system, from the tank to the injectors, had to be cleaned and several parts replaced. It's a simple mistake with a very costly outcome. Always double-check the pump handle; green is almost always for diesel.

[LaCarson]

From a purely financial standpoint, it's a disastrous error. The average insurance policy does not cover misfueling, as it's considered driver negligence. You are personally liable for the full repair cost, which typically ranges from $1,500 for a simple drain and flush (if the engine wasn't started) to over $5,000 if the high-pressure fuel pump is destroyed. This is one of those mistakes where a moment of inattention can wipe out your savings. The only cost-effective action is prevention: always confirm you have the correct fuel nozzle.