Misfuelling your car – a costly mistake

Putting the wrong fuel into your car can be a massive mistake. If the vehicle is driven, the engine can seize and parts of the fuel system may be destroyed. It can easily result in a write-off due to parts costs.
At Fleetcare, on average, a maintenance controller will take around 3 calls a week regarding misfuelling.

A diesel input hole in a vehicle is bigger than a petrol input hole, so more than likely these calls have been regarding a client misfuelling a diesel car. The pump for diesel is a lot thicker and often doesn’t fit into petrol engines however our maintenance team occasionally receives calls that this has happened. Often clients have just had a bad day, are in a rush or their minds are elsewhere.

Petrol Vs. Diesel. How do they work?

Diesel and petrol both have advantages and disadvantages when it comes to choice. It often depends on what the engine is being used for that will help the driver to decide what type of fuel engine would be best for the job.


Diesel is run off an internal combustion engine which uses glow plugs to ignite with heat compression. Diesel is a much heavier mixture and also very oily. Diesel engines have a lot more torque (pushing power) at lower revs and a diesel engine comes in both two stroke and four stroke versions.


Petrol engines use spark plugs to ignite and burn fuel to make an engine run. Petrol engines rev higher than a diesel engine. In most petrol engines, the fuel and air are usually pre-mixed before compression (although some modern petrol engines now use cylinder-direct petrol injection). Petrol engines must be geared lower to get the same torque as a diesel but since petrol engines rev higher, both will have similar acceleration speed.

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What is the cost of misfuelling?

For those drivers that notice the fault before starting the engine, the cost to a business is around $460. This includes the costs to flush the fuel system and change the filters, not to mention the wasted fuel.
However, if you are unlucky enough to drive away from the petrol station with the wrong fuel, the cost to a business can be significantly higher. Should major repairs need to be done from the resulting damage, pricing can range from $4,000 to $17,000 depending on the vehicle and damage. Average repair cost for this unfortunate error is $7,000.

What are the steps you should take after putting the wrong fuel in your engine?

Find out more

Find out more

It happens to the best of us. A minor lapse in concentration and we have misfuelled our vehicle. Before panic sets in, and to help prevent any further misfuelling damage, Fleetcare has a few steps to keep you calm and deal with the situation that’s at hand.

  1. Do not start the engine at all. If you’re at a pump don’t even start the car to move away to allow the car behind you in.
  2. Tell the service station attendant about your error and pay for the fuel dispensed.
  3. Disconnect the battery before attempting to move the car. Switching on the ignition to release the steering lock may feed contaminated fuel to the injectors. Even a small amount of the wrong fuel in your engine can require dismantling of the complete fuel system and replacement of expensive components.
  4. Call your road-service provider or a removal truck to transport the vehicle to a mechanic where they can drain the tank, clean the fuel pump and replace any filters.
  5. If you don’t notice the error until the vehicle has been driven, stop as soon as you can and call for assistance. The longer you drive, the more damage you will cause to your vehicle.

Car warranty and misfuelling insurance

Some insurers do offer misfuelling protection, however it pays to check that this is covered in your policy. Most, if not all car warranties, don’t cover misfuelling.
If the error is caught before turning the engine back over, the vehicle can usually be towed, drained, inspected and saved. However, this would be at a cost to the driver – most insurance companies would not provide misfuelling cover in this situation nor would any car warranty.

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Categories: Fleet Management, Fuel
David I filled a diesel vehicle with diesel fuel. When I went to pay with a diesel only card I was told that I had filled up with petrol and could not pay with this card. I said that I had filled up with diesel. The attendant checked the bowser readings and found that the litres and $ matched diesel so she changed the cash register to diesel so that I could use my diesel only card to pay. How many people have been have been caught in this situation by a faulty petrol station computer system? Be aware it may not be your fault. 7/08/2018 2:56:16 PM
Fleetcare Hi Anderley,

Thank you for sharing your experience with us. Should major repairs need to be done, pricing can range from $4,000.

We are glad to hear that you were able to sort this with your mechanic before any further damage could be caused, and at a great price.
28/07/2017 12:22:11 PM
anderley burden Husband accidentally put Vortex petrol - 60 liters instead of Diesel in our 2016 Kia Sorento 2.2ltr platinum. During the drive home, the car began to cough and splutter, threatening to stop. He soon realized his mistake. The wonderful people at Kia took over and took care of everything. A sleepless night was spent after reading all the stories on google. When we picked it up 24 hrs later we expected it to cost anywhere from $7000 upwards. When we heard the repairs that included an engine flush plus some minor parts replacements totaled $761.75. Service department noticed our relief and remarked that we must have been checking on google for the cost. Moral of the story is: Caution to those that believe what they read on the net. 21/07/2017 4:28:23 PM
Fleetcare Hi Charish,

Thank you for sharing your experience with us. Unfortunately, misfuelling is a common mistake amongst drivers.

We are glad to hear that you were able to sort this with your mechanic before any further damage could be caused.
7/06/2017 8:07:30 AM
Charish Kleinrahm I accidentally did this few days ago. I drove my husband's ute from the mechanic to bp petrol station before heading home. I put no ultimate unleaded instead of diesel, because they are the same color, black. And I was so stressed for some reason that's why I did this expensive mistake.
Fortunately. As soon as I finished filing up, I noticed I've put unleaded instead of diesel and did not start it. I rang my mechanic straight away and ask what should I do. Rob, the good mechanic of Kmart auto in morayfield, told me not to start it at all and he rang someone to tow my car. He fix our ute, he drain the fuel tank, flush it and put diesel. The cost of it all? $88 for towing $292 to have it fix.
Lesson learn: double check what fuel you are putting in your car. Don't rush.
2/06/2017 7:12:06 AM
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