Diesel in a petrol car vs petrol in a diesel: what to do

Misfuelling happens more often than most drivers realise, and it can happen to anyone at a busy forecourt. The two common mistakes are putting diesel in a petrol car, and putting petrol in a diesel car. Both need attention, but they are not equally serious. Understanding the difference helps you make the right call quickly and avoid turning a simple mistake into an expensive repair.

Diesel in a petrol car is the less damaging of the two, though it still needs to be dealt with properly. Diesel is heavier and oilier than petrol, and a petrol engine simply cannot run on it. In most cases the engine will struggle, misfire, or fail to start shortly after the wrong fuel reaches the system. Because diesel does not ignite the same way in a petrol engine, the damage is usually limited to the fuel system rather than the engine internals. The key is to stop, switch off, and not keep trying to start the car.

Petrol in a diesel car is a different story and is generally far more dangerous to the vehicle. Diesel fuel acts as a lubricant for the high-pressure fuel pump and injectors. Petrol is a solvent and strips away that lubrication, which can cause metal-on-metal wear inside the pump and injectors in a very short time. Even a small amount of petrol, or running the engine for only a few seconds, can cause significant damage to components that are costly to replace. This is why petrol in a diesel is treated as the more serious misfuel.

In both cases, the single most important rule is the same: do not start the engine. If the engine is already running, switch it off as soon as it is safe to do so. Do not turn the key again, and do not try to drive the vehicle even a short distance. Every attempt to start or run the engine pushes the wrong fuel further through the system and increases the risk of damage.

What to do right now

If you have put the wrong fuel in your vehicle, stay calm and follow these steps. First, do not start the engine and do not move the car under its own power. If you are at a service station, let the attendant know. Then call EEK Mechanical on <a href="tel:0800769000">0800 769 000</a>. We will arrange a tow truck to collect your vehicle from wherever it is, whether that is a forecourt, the roadside, your home, or a car park.

Your vehicle is transported to a NZIFDA-certified workshop, where manufacturer-spec fuel system recovery is carried out by qualified technicians. This work happens only at the workshop, never at the collection location, so you can be confident the job is done properly and safely. Costs vary depending on your vehicle, the distance involved, whether it is after hours, and how badly the fuel system is contaminated. Recovery is fully itemised, and you can see exactly what is involved on our <a href="/rate-card">rate card</a>.

If you are unsure whether the wrong fuel has gone in, or you are worried about the condition of your vehicle, it is always better to have it checked than to risk starting it. Our team is available 24/7 and can dispatch a tow truck to you at any time. Call <a href="tel:0800769000">0800 769 000</a> and we will take it from there.