A Driving Instructor's Blog

RobberThis article was originally published in 2013, but it’s been popular recently so I have updated it. I’ve also written a more detailed explanation about why fuel is priced in tenths of a penny, here.

I’ve noticed that sometimes – and I stress sometimes – the petrol pumps at my local garages jump by 1p after I’ve finished filling my car. I usually notice it if I’m trying to put a round number of pounds worth of fuel in – so if I’m aiming for £40.00 I’ll just hit it, and when I get inside the amount payable is £40.01. Looking on the web, other people have noticed it too, and they are putting it down to some sort of scam. But is isn’t.

There is a simple explanation – given here by Leicester County Council Trading Standards. They say:

Q. When I put the petrol nozzle back the meter clocked up one penny when I was not delivering any fuel, is there a fault on the pump?

A. Sometimes the price advances when you close the nozzle and return it to storage. This can be caused by the hose swelling slightly which allows a fractional amount of fuel to pass through the meter. Because of the high price in petrol only a very small amount of fuel is needed for the price display to change by 1 penny therefore this problem is much more prevalent now than it used to be. One penny’s worth of fuel only equates to a very small amount and is well within the permitted tolerances of -0.5% and +1%. However if the price increases by more than 1 penny please let Consumer Direct know on 08454 04 05 06.

Those tolerances mean that for every 1,000mls (litre) of fuel you pump, you can legally get anywhere between 995mls and 1010mls. If fuel costs £1.20 per litre, that means you might get 0.6p less fuel than you paid for, or 1.2p more. On a full tank in a standard car, that works out at up to 24p less or 48p more fuel than you actually paid for, respectively. I stress again that this is perfectly legal, and is due to the reliability and accuracy of the pumps. Coventry Trading Standards explains it this way. As Trading Standards say, it is well within all the legal tolerances.

A tick over of 1p is insignificant within this legally acceptable range.

Most of the time it is perfectly possible to put an exact value of fuel in and it doesn’t click over. In fact, it happened more back in 2013 – when the price of fuel was up around £1.40 a litre – than it does in 2017 (I haven’t noticed it recently). And yet people are still convinced that there’s a small bloke wearing a striped jersey and a mask sitting inside the pump doing it on purpose. It isn’t a scam, and it isn’t deliberate. It’s just a combination of maths and science.

If you’re worried about it, don’t put piddling amounts in your tank – fill the damned thing up once a week instead of putting a tenner in every other day. One penny on a tank full is a lot less significant than it is on each of four lots of £10.00. And it means you won’t keep snarling up the forecourts for the rest of us as you pay for it on one of your bloody Visa cards.

And one more thing – a tip, really. You often find that the nozzle has got well over 1p of fuel sitting in it when you lift it out of the holster – so turn it upside down to drain it into your tank before you pull the trigger. And do the same thing before you put it back. That should be enough to stop all the sleepless nights you’re having over those pesky 1p muggings you reckon you’re getting – you’ll be getting someone else’s fuel for nothing!

Why do pumps always jump by 1p?

They don’t. They just do sometimes, for the reasons I’ve explained above.

It never happens when I put in 20 or 30 litres of fuel, instead of £20 or £30

Actually, it can. But because of the 0.9p or 0.7p they tag on to fuel prices, aiming for a specific price instead of a quantity puts you close to the tick over point, whereas aiming for a round volume probably puts you somewhere half way between two points. Pumping 20L at 119.9p per litre will give a nice round £23.98, whereas £20 works out at 16.6806L of fuel. That 0.6ml is going to get rounded up.

It’s definitely a scam

No it isn’t. Do you really think they designed them with a line in the software that says:

if (ran == 0) then price = price + 0.01;

The 1p is just an occasional rounding up. It is not a scam.

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