Tip – pay attention to what fuel goes into your vehicle

Avoid a potentially damaging and costly problem if not rectified

What if petrol was put in a vehicle that required diesel?

Putting petrol in a diesel car is far more serious than putting diesel in a petrol car. The petrol will act as a solvent, damaging the fuel pump and other parts of the fuel system. If left unchecked, this could mean a costly repair of your car’s fuel system, or a complete replacement of the fuel pump, diesel injectors, filters and fuel tank. Putting petrol in a diesel car can cause serious damage to the fuel injection system and engine.

If you have already started or driven the car, stop it safely as soon as you can and turn off the engine to minimise damage. Call for roadside assistance for a tow to your nearest fuel station or service workshop to have a mechanic drain the fuel.

What if diesel fuel was put in a vehicle that required petrol?

The result of putting diesel in your petrol car is not quite as catastrophic as when it’s the other way round. The car will usually run roughly and the exhaust will be smoky. But it is still much better not to drive the car no matter which type of wrong fuel you’ve put in the tank. If you’ve ever compare petrol to diesel fuel, you will notice they smell different. They also feel different – diesel fuel is oily. Like oil, diesel fuel doesn’t evaporate like petrol does. Plus, diesel fuel is heavier.

If you had a petrol tank filled with diesel fuel, the fuel injectors in your engine would inject the diesel fuel into the engine’s cylinders. The spark plugs would fire, but nothing would happen after that. Because the diesel fuel doesn’t evaporate very well, the spark plugs would have nothing to ignite, and the engine would not start.

To solve the problem, you would need to drain all of the diesel fuel out of the petrol tank and refill it with petrol. This would be a time-consuming exercise. Then you would have to keep cranking the engine for a while to get the diesel out of the fuel lines and the injectors. Eventually the engine would start and run. There should be no damage if done as it is detected and not continue to try and drive.

Should you be thinking this: If diesel fuel won’t burn in a petrol engine, why does it burn in a diesel engine? There are two big differences between petrol and diesel engines:
First, diesel engines have no spark plugs.
Second, they have much higher compression ratios. When the diesel engine compresses the air during its compression stroke, the air gets extremely hot. The diesel fuel is injected directly into this hot air, and it’s hot enough to vaporize and ignite the diesel.