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