Weekend Lesson: Putting The Wrong Fuel In A Car ⛽ | Nimble

October 28th, 2022

It’s a common mistake that happens to the best of us: putting the wrong fuel in our car.

Maybe you slept in, missed your morning coffee and were in a hurry to get to work when you grabbed the wrong pump at the station. Or perhaps you borrowed your partner’s car and accidentally put petrol in a diesel.

Whatever your reason for filling up with the wrong fuel, it is important that you know what to do when it happens or the next steps to take.

Just remember, you’re not alone.

Whilst there is no exact figure as to how many people make the mistake each year, it’s common enough in Australia to have a business specifically created to deal with the problem.

Yan Van De Velde, the company director of Wrong Fuel Rescue claims his company rescues ‘thousands’ of stranded motorists each year.1

But at what cost to your bank account?

Especially when it can be avoided.

The following tips may just help you prevent getting yourself in that tricky situation and awkward small-talk with a tow truck driver all the way home.

Find out what type of fuel your car takes

First things first.

Make sure you check what type of fuel is right for your car.

Most cars will have the information you need in the handbook (if you still have that old thing). But don’t stress if you don’t because most cars have it on or around the fuel cap depending on the make and model of your vehicle.2

A majority of cars on the road take diesel or unleaded petrol which are two very different fuel types, for two very different engines. Like wine and beer, they should never be mixed so don’t try it at home folks.

LPG exists and is used, but these days only accounts for 2% of total automotive fuels sold in Australia3, so chances are, if you need this type, you will most likely know.

So now that you know you know what fuel you need, what’s the deal with all the different options?

Unleaded Petrol

There are different Research Octane Number (RON) ratings4 for fuel.

  • 91 RON is our standard unleaded here in Australia
  • 95 or 98 RON are our more premium options
  • 94 or 95 RON is classified as E10 (10 means it contains 10% ethanol) – this tends to be the cheapest option


There are two common choices.

  • Standard Diesel
  • Premium Diesel – reduces foaming at the pump, runs cleaner in the car engine and reduces black soot from the exhaust5

Better yet, if you want to forget the whole wrong petrol scenario, you could always upgrade your vehicle using a Nimble Personal Loan to purchase an electric car. It literally runs off large batteries so you can say goodbye to the fuel pump and hello to a recharge station.

What to do if you have put the wrong fuel in your car

First, just breathe.

Get your head together and don’t freak out.

Any rushed decisions could result in further damage to your vehicle so make sure you do the following:

1. Don’t start the engine

As long as you don’t turn the key or press the engine button, the damage will be kept to a minimum.6

2. Roll to a safe place

You are going to need to move your car away from the bowser. So put your car in neutral, release the hand brake and recruit the strongest person you can find (or the most sympathetic) and push your car safely away from the tank.

3. Call for assistance

Unfortunately this is not a job for even the best of us DIY-ers. You are going to need a professional who does this on the regular.

They are going to need to drain the fuel from your vehicles. If they are a service that is equipped to handle these car problems, they may be able to do it on the spot. Otherwise they might need a tilt tray to take your car somewhere that is safe and designed to do the job.7

4. If you have already driven off

So if you do leave the servo with a krispy kreme in one hand and the wrong fuel on board, you will know about it quick enough.

Your engine might start making some scary and somewhat offensive noises, and if you continue to keep driving (please don’t!), you may come to a coffee spilling halt further down the road.

Being quick to act is the key to this situation. The sooner you stop and call for help, the more chance you will have of saving your beloved beater.

What happens if you put petrol in a diesel car?

This is the most common refuelling mistake to make, resulting in severe engine damage if it is not rectified as soon as possible (by a professional).

Whilst a costly exercise which could set you back thousands in repairs,8 in 99.9%9 of situations it is able to be fixed. 

Acting promptly is essential to minimise damage.

So why does it happen?

It is much easier to fill your diesel engine with petrol (especially if you rock up to the bowser half asleep) than it is to do the opposite.

The petrol nozzle fits inside the filler for a modern diesel, making it quite easy to fill it up before noticing the error.

What happens to the vehicle?

When you add petrol to diesel fuel it creates a solvent that reduces lubrication and can cause serious damage to the fuel pump and fuel system within the engine of your car.10

What happens if you put diesel in a petrol car?

Now it really is much harder to put diesel in a petrol car but nonetheless possible for some.

How can it happen?

Generally, the diesel nozzle won’t fit into your petrol tank so if you’re trying to fill up and it’s just not working, step back and check your pump.

This kind of mistake normally happens when you mix up the labelling on a jerry can or accidentally fill up with the wrong type when filling them at a service station.

What happens to the car?

Diesel needs to be compressed before ignition whilst petrol ignites through the spark plug11 . This means that putting diesel in a petrol tank will most likely result in your car not starting.

However, if you have noticed you’ve made this error, don’t even try turning on your car or putting the key in the ignition. 

If you don’t prime the electric pump in the tank, you don’t circulate the wrong type of fuel, so it is much easier to drain and clean the tank.12

Ways to avoid putting the wrong fuel in the car

  • Pay attention when refuelling – always check the labels on the bowser so you don’t grab the wrong fuel
  • Avoid any distractions while filling up
  • Know what kind of car you have so you know what type of fuel to purchase – a quick search may help or if in doubt, call your dealer or mechanic
  • You can buy a device for your diesel car that prevents petrol fuel nozzles from fitting into diesel tank necks, whilst still allowing diesel ones

Will car insurance cover the repair costs?

The not so great news is that over 90% of Aussie insurance companies do NOT include filling up with the wrong fuel as part of their cover.13

Typical repair costs can set you back anywhere from $400 up to a whopping (hold your breath) $40,000 for certain models and makes.14

Make sure you check your insurance PDS to see if it is included long before you make this mistake (which hopefully we will prevent you from making).

If you do have cover, just check with your excess because if the damage is minimal, with the right early intervention, it may be cheaper just to pay for it without claiming on insurance.

Paying for the cost of damages

You have called the professionals and are waiting for someone to come out and assess the damage. Hopefully it is minimal if you follow our steps above.

If your wallet is feeling a little light, don’t panic!

Grab your smartphone and head to Nimble to find out what options we have available for your emergency roadside assistance.

For smaller repairs, you can apply for a Small Loan to cover any costs.

For larger repairs, you can apply for a Nimble Personal loan to ensure your ride can get back on the road ASAP.