Pump up your attention or pay



Mistakes at the pump can be costly.

Sometimes it’s not until your vehicle breaks down on a petrol station forecourt, or it sputters to a halt as you try to leave the station, that you realise you’ve filled your car with the wrong fuel. Either way, it’s a truly frustrating, time-consuming and costly experience. But, it’s not something to feel embarrassed about, as it happens all over New Zealand on a regular basis — so much so, that companies now exist to come to our aid and get us back on the road after filling up with the wrong fuel. There are even devices that can prevent this from happening in the first place.


Motorists with multiple cars — or those who drive fleet pool vehicles regularly — are probably the most likely to make the mistake of filling up with the wrong fuel. To avoid this, all it takes is just a quick double check of the fuel that’s required for the vehicle, often shown on a sticker inside the petrol flap.

It’s more common for motorists to put petrol into a diesel system than the other way around and, unfortunately, it also has the potential to be the most damaging and costly error to make. Diesel fuel pumps operate on very fine tolerances and they’re lubricated by the viscose diesel fuel. If you run petrol through a diesel system you’ll strip the lubricant, causing the pumps to run dry and ultimately damage them from the metal to metal contact.

If your vehicle has a common rail (CRDi or HDi) diesel engine, it pays to be extra cautious as repairs or replacements after filling up with the wrong fuel can be very expensive.

If the fuel pump is damaged or contaminated fuel reaches the common rail system, you’ll need to pay for the fuel pumps, injectors, fuel rail, filters and tank to be cleaned out and you might even need replacements.

The process and cost of repairs will depend upon the type of vehicle you have and how long you’ve been running or attempting to run your car on the incorrect fuel.

In worst-case scenarios, bills can be thousands of dollars — especially if a large chunk of the fuel system requires replacement and repairs to the engine are necessary.

If your vehicle is under warranty, it also pays to consult the manufacturer or the warranty company. They may have guidelines or policies on the cleaning and replacement process you should follow to ensure you remain covered and to prevent further issues.

Many vehicles now have an electric, low-pressure pump in the fuel tank that operates the moment you turn on the ignition. So if you’ve just put the wrong fuel in your car and turn on the ignition, it will soon be circulating its way through the fuel system, causing damage in a matter of seconds. Leaving the ignition off gives you a good chance of minimising the damage and you may need only to get the tank drained and topped up with new fuel to be able to get you on your way again.

If you have to learn the hard way, hopefully it’s this option.

Diesel users will be aware they need to unlock the pump before using it. Picking up a petrol pump without having to unlock it first should automatically trigger warning bells. This may explain why fuelling your petrol vehicle with diesel is less common, but it still happens.

After putting diesel in a petrol car you’ll probably find that the engine may just simply fail to start or if it does, it’ll soon sputter out afterwards. In some cases your car may continue to run but you’ll certainly notice that it’s not running as well as usual. Typically your car will display symptoms as well, such as pinking (a noise from the engine), exhaust smoke and a loss of power.

If operated for extended periods of time, you also run the risk of internal damage to the engine. For most cases, repairs usually involve draining the fuel, changing fuel filters, flushing fuel lines and possibly cleaning the spark plugs and injectors before filling up with the correct fuel.

If you ever fill up with the wrong fuel, there are companies throughout New Zealand that can come to your rescue — as long as you haven’t touched the ignition. For a very expensive fee, they can suck out the contaminated fuel from your car’s tank, letting you refill and hit the road in no time.

A petrol fuel nozzle is a cheaper alternative that prevents you from actually putting the wrong fuel into your tank in the first place. Products available in New Zealand go by the name of Dieselhead, which simply fastens in the place of the original fuel cap. The filler will only receive a diesel filler nozzle and won’t fit the smaller petrol nozzle that’s at service stations. You don’t have to worry about putting the wrong fuel in your car again — plus it even comes with an external cap to stop unwanted fuel or water drops from entering the filler when activated.

Product review – Car Products Tested


Stop putting petrol in a diesel! We test the Diesel Head misfuelling prevention device…

 By Chris Davies on July 4, 2012

Diesel Head – What’s That?

DieselHead misfueling device test and review001

We’ve all seen it or experienced it at some point in our life – the wrong fuel being put into a tank. Usually, it’s petrol in a diesel, because it’s nigh-on impossible to get the wider diesel nozzle into petrol cars.

So, the implications of misfueling your car? Diesel Head’s website have a few good suggestions which include loss of warranty, the huge cost of replacing expensive parts like your fuel pump, paying for two tanks at todays diesel prices will slap you hard at £160+, and then there’s all the other stuff like being late for a flight, or an interview (should you actually manage to secure one in this economy).

Then there’s the physical feelings that come with it. Oh the embarrassment! People are already seething at the cost of diesel, so you causing a jam as a huge queue of irate fuel-thirsty cars line up behind your broken-ass vehicle, will not make for a happy mob. Even worse is the realisation of what you’ve just done; much like a swift kick to the privates, the colour drains from your face and along with it comes the nausea. Not nice.

So, you get the point anyhow; misfueling is properly pants. Worry not though, we’ve just tested Diesel Head’s Misfueling Prevention Device – and it’s fab!

Firstly, let’s deal with well the Diesel Head is made. Taking it out of the box, is looks as if the part that attaches to the filler hole is plastic, but actually it’s highly polished metal. It’s heavy and chunky, but also beautifully crafted, and looks sweet as when fitted to your car.

DieselHead misfueling device Quad 001

How does the Diesel Head work?

As you push the diesel nozzle in, two catches open which in turn releases the gate so the nozzle can pass. Simple, but effective.

The cap is really robust too. It’s much like what we often refer to as Playmobil® plastic. Tough and durable, it’s not going to break or wear anytime soon.

Simple to install, the Diesel Head will fit the vast majority of vehicles. We fitted the supplied Lockable unit to an imported Mitsubishi Pajero, and it went on fine. However, a large degree of patience was needed because screwing the tiny screws into place with an allan key within the confines of the petrol car enclose is hugely fiddly.

When we’d nearly finished fitting the Diesel Head, but then realised we needed to use the (included) longer grub screws as the others weren’t biting – and therefore starting all over – one of our testers ended up a gibbering wreak, crying and cursing until we slapped him back to reality.

When it’s eventually fitted though, it not only looks absolutely great, but buying the Lockable version (just £5.00 more) will give even more peace-of-mind. Before we forget, the Diesel Head also comes with a rubber insert in case you need to fuel from a fuel can (gas can).

DieselHead misfueling device test and review002

Is the Diesel Head effective?

Yes. You’d have to absolutely ram a petrol nozzle in as hard as possible to break the little openers off, and by that point you’d certainly know something was wrong (unless you’re very stupid). At the same time, a diesel nozzle slides smoothly in with zero problems.


For many reasons, you should go buy and fit a Diesel Head to your car. At around £40.00 it may seem like you’re just swapping expensive fuel caps, but remember; It only takes one time when you’re tired or in a rush to fill up with the wrong fuel – Prevention is better than cure. The cure being, in this case, the Diesel Head.

SCORE: 9/10

+ Good quality materials, excellent prevention, looks good
– Somewhat fiddly to fit

Battle of the Sexes!!

Research shows that men are more likely to misfuel than women.
No matter who does it, be prepared to dig deep to get the diesel vehicle fixed.

“It was about 9pm. I was pregnant, nauseous and very very tired. My husband had JUST completed a gruelling two-day multisport event. All that was left to do was fill the borrowed ute with fuel, and head to the holiday house we had rented for the weekend. And that’s when hubby realised he had put petrol into the borrowed diesel ute. I am embarrassed to say it now, but  I remember  I began to cry! Neither of us had the energy or brain power to deal with the problem. We called our roadside help company, and the nice man helped us out while I stayed huddled in the cab hoping I wouldn’t throw up. Hideous!

Hayley Redpath, Matawai 

I was a nurse back then, and I had just finished a nightshift at the hospital when I decided to refuel. Our car was fairly new, and I filled it myself at the petrol station. But I put petrol into the diesel tank. I didn’t even know I had done it. I drove out and then putt putt putt, it stopped. I was almost home so it wasn’t a huge problem that morning. But it became a huge problem later on because getting the problem fixed meant we had no car for a while. We had two young children and were reduced to using public transport. It cost about $300 to get the car towed, the lines flushed, and the petrol drained.

Jason Ward, Central Hawke’s Bay

 “I started a new job in vehicle sales and on my first day was given a company car which was a small car with a diesel engine. For me that was an unusual combination. At the end of my first day I left work in heavy rain and had to go directly to a gas station where I filled the car. I inadvertently put petrol in it because it seemed like the obvious thing to do given it was just a small car (which in my experience would normally have a petrol engine). As soon as I pulled out of the gas station the car stuttered and stopped. I immediately realized what I’d done and I was mortified. I had to walk back to the dealership in the pouring rain and it cost the company a lot of money to rectify the damage done by running petrol through the system.

Cameron Brock, Palmerston North