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Accidentally put petrol in your diesel car?

Turning up at the petrol station with a million other things on your mind, it’s all too easy to grab the wrong nozzle and pump ten litres of petrol into your diesel car before you’ve even realised what’s happening. Believe it or not, this is actually an incredibly common mistake that people all over Perth make every day. That pesky petrol nozzle just fits into the diesel filler all too easy.

Putting the wrong fuel in your car isn’t the end of the world, and just about all of us have done it at least once. What matters now, is how you deal with it! You might have heard that a small amount of petrol in a diesel car is totally fine, and you can just fill the tank up and carry on your way.

Man Looking at Petrol in Diesel Engine

The truth is it’s a little more complicated than that. Sure, you can fill the tank up with diesel and hope for the best. But how much is a replacement engine going to cost you? Will your insurance cover it, or will it count as gross negligence and you’ll be left with an expensive paper weight (your now dead motor) and the shell of your car.

Before you make any rash decisions, consider the information below.

Or, take the safe route and call Fuel Swap today. We’re experts in safely and efficiently removing the wrong fuel from your car, so you can get back on the road with complete piece of mind.

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(EPA/DWER Compliant)

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What happens if you put petrol in a diesel car?

There’s two main differences between diesel and petrol. As a fuel, diesel takes a lot more to get it to burn, whereas petrol burns incredibly easily. Secondly, diesel is essentially an oil, which means it has great lubricating properties—which the motor relies on to keep components working right. Petrol on the other hand, has no lubrication properties, and will strip protective coatings from the metal engine components.

What does this mean? It means you’ve got two main things that can go wrong if you put diesel in a petrol car.

1. Petrol’s (anti) lubrication properties

Your diesel car’s fuel pump needs diesel to keep it well-oiled, essentially, and to prevent the intricate metal components getting hot and wearing out. When petrol runs through this pump instead, the metal-on-metal contact causes the pump to get hot, and you’ll eventually get fine metal shavings throughout your motor. This can spell absolute disaster for your engine, costing thousands of dollars in repairs as the fine metal particles ruin tight clearances and prematurely wear expensive parts.

So if you’ve filled up with petrol, don’t even turn the ignition on! This will prime the fuel pump, and can stuff it without even turning the car on. With a modern diesel, the pump and engine parts are even more sensitive than ever before, and this common mistake with a late model diesel could cause serious damage.

2. Petrol’s lower combustion temperature.

Basically, petrol catches fire with much less encouragement than diesel. A diesel engine is carefully calibrated for the fuel to explode at just the right time, giving you power. When you add petrol into this mix, all of a sudden that combustion event is happening too soon. Much too soon. This can wreak all kinds of havoc, from small explosions in other parts of the system, to engine combustion occurring too early in the cycle and bending critical engine parts. Worst case scenario? New engine (well, excluding the whole thing catching fire).

How much petrol is OK in a diesel car?

The majority of car manufacturers state that no amount of petrol in their diesel cars is safe, and we can’t blame them. Can you imagine the law suits if they said it was fine, and it wasn’t? 

Generally though, experts in auto business say 2% or less petrol in a diesel car is safe. In a newish diesel ute with an 80 litre diesel tank, 2% is about 1.6 litres of petrol.

So if you’ve only squeezed the petrol nozzle for a moment before realising—you should be ok to top up with diesel and carry on your way. Just pull out your phone (maybe inside the servo, rather than at the bowser!) and double check the maths. 

If you’re unsure, give us a call. We’re experts when it comes to these things after all!

Can I drive with petrol in my diesel car?

Like we talked about above, technically—you can. But should you? If it’s only a tiny amount of petrol, say a litre or so, two at the absolute max, in a full tank of diesel, there’s a possibility your car will be fine. Over two litres though, there’s a possibility you’ll ruin your engine and write off your car, which is why we stand by getting that petrol drained out, and fresh diesel pumped in.

Petrol in Diesel Engine

So, what should I do if I put petrol in my diesel car?

First of all, just breathe. Make a note of exactly how much petrol you’ve just pumped in, and give us a call. We’re always happy to help out, and can tell you exactly what to do next. If it’s safe, we’ll ask you to drive the car into a bay—a short distance will be ok—and then you can make the call about what to do next. 

But don’t leave the car running, and don’t drive a metre more than you have to!

Once you’ve calmed down, and let your boss know you’re going to be late, or your partner you’ll be home a little later than usual, you’ve essentially got 3 options.

1. Risk it. The option we DON’T recommend.

Option 1, fill the car with diesel and hope for the best. If you’ve done the math and you’re willing to take the risk, or can easily afford a new car, then so be it. Don’t say we didn’t warn you!

If you’re choosing to hope for the best based on the cost of getting the petrol pumped out and diesel pumped in, then consider this. That cost might seem like a lot right now, but how much is a new car worth? Could you afford to replace your car if this gamble doesn’t work out?

wrong fuel help rescue fuel swap

2. Get your car towed to a mechanics workshop for a drain, flush and refill.

This is a surprisingly common option, that seems mostly pushed by insurance companies that want you to use their towing services and preferred repairer’s mechanical services.

Getting a tow and then employing the services of a mechanic to drain your tank, however, are going to cost at least as much as a Fuel Swap callout—while being far less convenient. With how quick we can get out to you and get you back on your way, there’s really no reason to need to have your car towed to a shop.

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3. Fuel Swap comes and does things the right way.

We’re a local Perth business dedicated to helping get you moving again. We’ll be out there as soon as we can, which won’t be long, to get the petrol out of your tank and get good clean diesel back in. You’ll be on your way again in no time, with the surety that your engine is not going to die at any moment and cost you thousands of dollars in repairs.

If you’ve put petrol in your diesel car, and don’t fancy your car’s chances of magically transforming into a petrol engine, give us a call today.

swapping wrong fuel to right fuel

Here’s what our customers say

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We have 5 stars Google Reviews from 180 clients

Absolutely brilliant service by Matt. Prompt, reassuring, helpful and fixed the job in minutes. Highly recommend Matt and Fuel Swap to anyone and everyone.

Sally Stott

Amazing support from Matt of Fuel Swap! Came out well within the time promised on a Sunday afternoon, was clear in setting expectations up front, professional and mail Ted a very clean safe environment to deliver the service. No hesitation in recommending their services when you make a mistake like mine of putting petrol in the wife’s diesel Prado!

Amazing Van Clan

Matt was very professional and knowledgeable. He got me out of my sticky situation in no time with great attention to detail and respect to my family and vehicle and the business property owner he had to perform his magic on

Allan Warneford

Matt was extremely prompt and very professional giving us some comfort in our hour of need and stupidity. No fuss, Matt just got on with it and let us know what he was doing every step of the way. He even followed up th next day. A rare thing these days with such good customer service. Awesome thank you

Michael Ford

We were extremely happy with the service provided by Fuel Swap. We dealt with Matt, who was professional and explained everything including pricing upfront. Matt arrived on time and did a fantastic job. I would recommend Fuel Swap to all of my family and friends

Kylie Barron

Accidentally put petrol in my diesel and called up Matt from fuel swap and he was very prompt and professional and had me back on the road within the hour.

Jayden Brown


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