Note: If you’re looking for information about the Misfuelling Prevention Device – as seen on Dragons’ Den – click here.

More than 50,000 RAC members put the wrong fuel in their car in 2007, according to a report released by the breakdown company. 50,000 drivers – and that’s just the RAC members who requested breakdown assistance following their misfuelling mistake…

As a driver of a hire van, you are probably more likely than average to put the wrong fuel in your van – especially if you normally drive a petrol car. You may be busy and pre-occupied with driving a large, unfamiliar vehicle – and using the petrol pump is probably a deeply-ingrained habit.

Unfortunately, putting petrol into a diesel engine can damage it severely. At best, you will have to pay for a mechanic to pump out all of the fuel from the vehicle – at worst you will cause thousands of pounds worth of damage to the engine.

Whatever happens, your rental company will hold you responsible for any costs resulting from you misfuelling – so it pays to be careful.

Here are some helpful tips from the RAC for drivers of diesel vehicles:

1. UK diesel pumps are always black or yellow (petrol pumps are usually green).
2. Many rental vans have a label near the fuel filler cap telling you what fuel to use – check for this before you fuel.
3. Petrol nozzles are smaller than diesel nozzles. If the nozzle seems unusually loose when inserted into the filler neck, check again that you are using the right fuel. Diesel nozzles will fit easily but without space around them. Petrol nozzles will be noticeably looser.

Here’s what to do if the worst happens:

1. Don’t start the engine – don’t even put the key in the ignition, as some vehicles start pumping fuel before the engine is started.
2. Call the breakdown service provided by your rental company. Follow their advice exactly.
3. Be prepared to pay a charge for having the fuel pumped out of your vehicle. If this is the worst that happens, count yourself lucky!
4. You will of course lose the fuel you have just paid for when it’s pumped out – it will be contaminated with the correct fuel and completely unusable by anyone.

If you have started the engine and driven the vehicle before realising you have put the wrong fuel in, then stop the engine as soon as possible and call for breakdown assistance. If you’re lucky you will just need all the fuel pumping out of the vehicle and there will be no engine damage.

However, it’s possible that you will have caused serious damage to the engine. The main reason for this is that petrol does not have the oily, lubricating qualities of diesel. This means that using petrol can cause accelerated wear and overheating damage in a diesel engine – bad news.

Finally, most of these comments apply to putting diesel into petrol engines, too. The only difference is that you shouldn’t be able to do this. Diesel nozzles are wider than petrol nozzles and don’t fit easily into petrol filler necks – so if you are having to force a fuel nozzle in, stop. You will be using the wrong fuel.