Drivers could save up to £162 a year on petrol thanks to a satnav device that directs them to their nearest and cheapest pump.

According to TomTom, around 41% of drivers routinely drive out of their way trying to find the cheapest petrol.

But its latest gadget, the Go Live x40 satnav system, aims to help drivers save time and money by directing them to the cheapest and nearest petrol station.

The device constantly tracks petrol prices depending on the car's location and automatically updates to tell drivers where the cheapest fuel is, as well as telling them the quickest way to get there.

Tom Brown from TomTom said: "Fuel prices are fluctuating all the time and this can affect everyone's day-to-day living costs. Our new device aims to help motorists cope with this."

Go Live x40 launches in mid-November, but Observer Cash has teamed up with TomTom to give one device away to a lucky reader. Details of how to win will be in Observer Cash this Sunday (November 2).

In the meantime, tell us how much you are paying to fill up your car by joining in with our interactive petrol price map. Email us at petrol.prices@observer.co.uk, with the cost of a litre of unleaded or diesel (don't forget to specify) and your location, and we'll add it to the map.