Wrong fuel: What to do if you put diesel in a petrol car or petrol in a diesel car

This is a problem that might make you think about whether it’s even real or not. However, it’s way more common than you can imagine. The modern diesel engines being silent as ever and a few older petrol engines sounding as loud as diesel, it becomes hard to distinguish. Most of the cars don’t even come with external badges and most of the time the fuel pump employees make a mistake. This is what happened to a Karnataka MLA, whose brand new Volvo XC90 got filled with diesel instead of petrol.

Wrong fuel: What to do if you put diesel in a petrol car or petrol in a diesel car

The horrific outcome of putting the wrong fuel in your car is something we’ve all grown up listening to. But, imagine if you’re in a hurry and you just let the employee of the fuel station know that you need INR 500 worth of fuel, missing to specify which one, only to later realize the wrong fuel has been filled. What would you do?

High precision petrol engines would choke up if filled with diesel and similarly modern diesel engines are also extremely sensitive to fuel quality. These incidents could damage your engine easily. However, if you realize your mistake quick enough, you could save your car. Here’s how.

Wrong fuel: What to do if you put diesel in a petrol car or petrol in a diesel car

Symptoms of diesel in a petrol car

Wrong fuel: What to do if you put diesel in a petrol car or petrol in a diesel car

So, how and what could go wrong when you put diesel in a petrol car? Fundamentally, diesel is much heavier than petrol and therefore relatively more oily. Initially, it is bound to impact the fuel filter. The fuel filter will clog up almost immediately and your car should begin to stutter and stall. Next, your spark plugs will foul up with soot build up because diesel will get mixed with petrol. At this point, your car will emit a lot of white smoke and ultimately lose all its power and come to a standstill.

Symptoms of petrol in a diesel car

Wrong fuel: What to do if you put diesel in a petrol car or petrol in a diesel car

Diesel engines are way harsher than petrol engines when it comes to the wrong fuel. Putting petrol in a diesel car will burn a deep hole in your pocket as they are equipped with technology such as the fuel injection pump that is dependent on the diesel’s lubrication properties to function. Even the rubber seals in the diesel engine don’t welcome the high cleaning, drying properties of petrol. It’s even difficult to diagnose that petrol is filled in your diesel engine. The symptoms expected is that the car will emit black smoke due to the unburnt fuel, eventually leading to a complete halt, post which the car will not start.

What to do if you’ve put in the wrong fuel?

The moment you realize you’ve put the wrong fuel, the ideal situation would be that you haven’t started your car yet. If you’re in this position, the next thing you need to do is disconnect the main fuel line for the engine to the tank. You might need a mechanic at this point. You need to basically access the tank using a hose, if possible, through the filler cap. Once you’ve reached the filler cap, try to syphon off as much fuel as possible. Drain whatever is left through the main fuel line.

Once, you’ve drained out as much fuel as possible from the car, crank the engine a few times by turning the key to pump out any remaining fuel. Don’t worry, your car won’t start. The fuel should drain out of the main fuel line as the engine cranks up. Post this, fill about two litres of the correct fuel and crank up the engine again to clean up the lines. Once, you’re sure all the fuel has been drained out, you may connect the fuel line back. Then, fill up your tank with the correct fuel and remember to ass an additive to clean the injectors for the diesel engine.

For a petrol engine, you’ll need to change the fuel filter and clean the spark plugs as well. With the diesel car, do open the drain plug at the bottom of the filter and drain out any fuel remaining in the filter as well. Thereafter prime the vehicle using a manual diesel pump and start your car.