Penny causes confusion

ARE THE petrol pumps pinching pennies from your pocket?

It is particularly noticeable if you fill a car up to round amounts such as £20, maybe because this is how you watch your spending or to do with work expenses. Either way, it seems that nearly every transaction will have an extra penny or two added to it, but how does it get there?

A little bit of research on the internet reveals blogs, videos referring to it as ‘the ghost penny,’ groups on a social networking site entitled ‘I hate going over by 1p at the petrol station!’ And some interesting theories and reasons behind the mysterious penny.

One website claimed that the one pence was to encourage customers to put in more fuel to try and get to a round amount again and therefore spending more money.

Trading Standards often receive complaints from customers who find that on replacing the nozzle in the pump that the price indicator adds on an additional 1p.

The measurement of fuel in a petrol pump causes a ‘pulser’ to rotate and send a signal to a computer. The customer display shows the quantity delivered and the price as calculated by the computer.

Because the price of petrol is very high, a very small movement in the pulser can be enough to trip the price indication on the pump by a penny. This represents only a very small quantity of fuel, roughly a teaspoonful.

Trading Standards told us that the pump uses a meter which physically measures the amount of fuel passing through.

A device attached to the meter converts the movement of the meter into a digital signal, which drives the quantity indication – ie the litres.

That indication is then converted into an amount of money, based upon the price programmed in, which often ends in .9 of a penny. This means the price to quantity calculation is not as straightforward as if it were in straight pence.

The amount of fuel which equates to a penny used to convert well, when the number of 0.01s of a litre - which the pump displays - when the price was lower, but as the price value has exceeded the .01’s of a litre value, the conversion rounds the price, and because the digital signal is also rounded, sometimes the price literally cannot stop at some values and will go consecutively say from 9.99 to 10.01 due to rounding.

A spokesperson from Trading Standards said: ““It is a complex issue; pumps are mechanical machines which have limitations and can go wrong. The metering technology is well known and is very trusted technology and most folk get what they pay for; its just that the technology has been developed with prevailing prices which have suddenly gone up lately, so in a way the technology has been left behind.

“The public should be reassured that they get what they pay for in all but a few occasions.”

The result is that nothing can be done about the penny but garages will often ‘let customers off with one pence.