What to do when you fill up with the wrong fuel?

If you realize that you have accidentally filled up with petrol instead of diesel, stop refueling immediately and, most importantly, do not start the engine. If you’ve only filled a small amount of petrol, you might be able to save the situation. At fuel stations, you can find additives that increase diesel lubricity. Pour the additive according to the instructions into the tank and top up with diesel. After driving an additional 100 km, top up with more diesel to dilute the mixture.

The safest solution is to have the tank drained and flushed by professionals. Do not attempt to drain the fuel or make any complex modifications yourself, as this could cause further issues. Did you fill up a full tank of petrol in a diesel car?

Do not turn on the ignition or start the engine to prevent the fuel pump from running and pushing petrol into the fuel system. Don’t even open the driver’s door, as some cars activate the pump when the door is opened. Contact a specialist service and have the tank flushed. If petrol enters the fuel system, the vehicle will lose power, and the engine will shut down. In such a case, it is necessary to visit a service where they will clean the fuel system and replace the fuel filter. Did you fill up with diesel in a petrol engine?

This situation is less likely due to the narrower opening of petrol tanks, but it can still happen, especially when refueling from a jerry can. Diesel can cause more severe damage to a petrol engine than the other way around. It will be necessary to replace the oil, spark plugs, fuel filter, and in the worst case, the catalytic converter or petrol pump. In turbocharged engines with direct injection, diesel can clog injectors and fuel lines. Did you fill up with petrol with a lower or higher octane rating?

The octane rating indicates the fuel’s resistance to knock under compression in the engine’s cylinder. Most fuel stations offer fuels with an octane rating of 95 and 98. If you fill up with fuel with a higher rating, nothing will happen. However, filling up with a lower rating can result in slightly reduced performance and increased fuel consumption, but the car won’t be significantly damaged. Did you accidentally fill up with E85 ethanol or B100 biodiesel?

Modern cars are usually adapted to fuels with a certain biofuel content, but E85 petrol (containing 85% biofuel) and B100 biodiesel are not suitable for standard engines. E85 ethanol can cause wear on valve seats and corrosion, while B100 biodiesel can cause compatibility issues in modern diesel engines, and long-term use is not recommended.