Motorists have pondered this question for years: how long will a car keep running when the fuel gauge shows empty?

Some manufacturers provide a comfort zone for motorists so that even when the fuel gauge or digital read-out says zero there is still a reserve of petrol or diesel fuel in the tank.

Other makers opt for a more refined measurement of what near-empty means using digital displays that offer a countdown of how many kilometres it is still safe to drive winding right down to nil.

As a rule of thumb it’s worth noting that most cars will run a further 50 kilometres even with all the warning signs activated.

Car clubs advise against testing these limits since the terrain of a particular journey and the often irregular shape of a modern car’s fuel tank can distort readings.

This means the tank can be more than half empty when the gauge is showing more. Even high-tech gauges rely on a simple floater in the petrol tank which is attached to a resistor. The floater moves up and down and records the actual level of fluid by measuring electrical resistance.

Experts recommend checking the owner’s manual to find out the exact tank volume, and next time the gauge shows empty they advise owners to fill up the car and make a note of the number of litres needed to brim the tank.

Deducting this figure from the volume stated in the manual provides a handy reckoner of just how far the car can be driven before hitting empty.

Do you drive around with the fuel light on? How long has it lasted you and how far have you driven? Let us know!