'Hypermiling' is aimed at bringing down fuel costs for motorists.

The term has grown in popularity after being started by an online community group known as 'hypermilers'.

According to the Mirror, drivers who have used the technique have saved on fuel beyond their car manufacturers' belief.

Hypermiling is a new trend to save drivers money and fuel

However, the controversial process could be unsafe.

A statement on the Hypermiler website said: "Hypermiling, as with any other form of driving technique, can be dangerous if used on the wrong road and in unsuitable traffic conditions.

"Please always be aware of other road users and do not endanger yourself or others for the sake of saving a few miles per gallon.

"We encourage safe and considerate driving."

What is hypermiling?

Hypermiling is a type of extreme, energy-efficient driving, which aims to get the most mileage out of every litre of petrol.

Instead of opting to spend money buying the most economical car, the concept is to drive your current car as economically as possible.

Hypermilers claim certain techniques are able to help cut back on fuel usage and costs by up to 40%.

M4 traffic

Hypermiling methods

Switching the engine off

Turning your engine off after you've built up speed will obviously save fuel.

But this also means you will lose your power steering, can't accelerate away from problems and might well have your braking compromised.

Drafting

Drafting is one of the more common techniques used by hypermilers - and is also among the most controversial.

It involves sitting close to or slipstreaming behind the car in front.

Estimates suggest it can save as much as 40% of petrol.

A lot of a car’s energy is used in "pushing" through the air, which becomes harder the faster you go. If another car is doing that for you, then you need a lot less petrol to maintain speed.

But obviously there is a safety risk as your visibility is reduced and it also cuts the amount of time you have to react to hazards up ahead.

Seven other money-saving tips

1. Get rid of unnecessary weight: Reducing weight is free and gains performance and economy, so take out all of the clutter from your car.

2. Go slow, go long: Driving at between 50 and 60 miles an hour is generally the most petrol efficient way to get from point A to point B. It can save you up to 40% fuel on journeys

3. Smoother is better: The less pressure on the accelerator, the less fuel you're using – avoid sharp braking (or let the engine slow the car naturally) and focus on the road ahead to keep your accelerating as smooth as possible.

4. Keep your car properly serviced: A well-maintained car is up to 10 per cent more efficient than one that has been allowed to fester in its old oil.

5. No air con under 40mph: Open a window instead. That said, if you're going fast the drag of an open window uses more energy than air con, so switch to that if you need to stay cool, although ideally on “recirculation” mode.

6. Ditch the drag: Roof racks off when they're not in use everyone. In fact anything removable sticking out of your car that you don't need should ideally go.

7. More air, less petrol: Under-inflated tyres are less efficient, make sure yours are topped up to the manufacturer's recommended levels.