If you haven’t found yourself puttering to a standstill with the Reserve Fuel icon lit up, you’re either very conscientious, or you haven’t been driving all that long. Occasionally running out of gas is one thing, but regularly hitting your reserve can have potentially serious consequences, for your car’s components – and even for your safety.

Understanding your reserve tank

When it comes to running out of juice, the term 'reserve tank' is sometimes used – but this is something of a misnomer; very few vehicles have a separate tank for emergency gas. Rather, the reserve light pings on when your gas dips below a certain level.

How far can you go on reserve fuel?

There is no industry standard on how far a car can travel on reserve fuel, but as a rule of thumb you can expect there to be 10-15 per cent of a full tank when that ominous light flicks on. Even if your math isn't so good, you should be able to work out roughly how much mileage you can expect before you shudder to a halt. Naturally, this calculation is more accurate if you know your vehicle's MPG figure – although there are still a few ifs and buts.

Driving style and conditions

If you're the kind of 'assertive' driver who enjoys quick acceleration and higher speeds, you can expect your last drop of gas to burn off pretty quickly. The same is true if you're fond of hard cornering and sharp braking.

Additionally, if you're carrying a heavy load or have low tyre pressure, you may not make it as far as you'd hoped.

And if you're route to the gas station features hills, you could run out of juice even sooner. Running up inclines burns more fuel than when you’re on the level, and the angle can even prevent the reserve fuel from reaching the gas pick-up device.

Don't even think about it…

The auto forums are full of out-of-gas stories. Don't be tempted to 'see how far you can get' on your reserve fuel. Running your engine dry is bad for the components, and in an older car may require a full engine bleed before you can restart it.

Filling up by the roadside with a jerry can also be a bad idea: any kind of activity by the side of a busy road is hazardous – but especially so when it involves flammable liquids. And let's face it, running out of fuel is entirely unnecessary, unless you take a seriously wrong turn in the desert somewhere.

Keep your tank at least one quarter full

Aim to keep your tank at least a quarter full at all times. For long trips, buy a full tank and work out where your next fill-up will be.

Let’s not fuel the myths

But if you do happen to find yourself running on vapour, there are a few untruths you should be aware of. Some people believe that running low will mean your engine sucks up any debris that may be sitting at the bottom of your fuel tank, potentially causing damage to your engine's moving parts. This is simply a myth – today's fuel systems feature at least one fine grade filter, while larger particles are caught by a special gauze sock protecting the gas pick up nozzle.

Another myth purports that continually running with little fuel leaves large air spaces in your tank, in which corrosion can take place. This was a worry years ago, when most tanks were formed from pressed steel. Today's cars feature much more durable plastic tanks, in which corrosion is, of course, not an issue.

Not convinced? Here are some more reasons why you shouldn't run low on gas:

• Your fuel gauge might not be accurate. It should be thought of as an estimate, not a hard-and-fast measurement.
• Running out of fuel may damage your catalytic converter.
• Plenty of fuel in your tank helps protect your fuel pump. Low fuel can mean the pump sucks in air, which creates heat and may damage the pump. Gas essentially acts as a coolant for your electric fuel pump, which can be expensive to repair or replace.
• Running out of gas could put you and others in a dangerous situation. You could find yourself in a remote location, far from a gas station, or you could stop running on a busy road – which carries obvious risks. Additionally, your airbags won’t function if the engine is off.

So the next time your Reserve Fuel light blinks on, head to the gas station. Better still, fill up long before you reach the bottom quarter of a tank.