Does heavy accelerating use more fuel?

Posted 10 April, 2025 Sasha Oelsner

In the past two years, the number of drivers spending more than $100 a month on fuel has doubled, according to RAA.

So, here are a few tricks to help make your petrol go the extra mile.

Putting the pedal to the metal

Both heavy acceleration and hard braking cause the engine to work harder, resulting in your car consuming more fuel in a short amount of time.

Monash University Accident Research Centre studied the difference between aggressive driving and using smoother techniques behind the wheel. Some drivers reported up to a whopping 30 per cent reduction in fuel consumption when using the smoother driving techniques. The techniques included avoiding high engine revolutions per minute (RPM) and hard braking at intersections and becoming adept at ‘gliding’ through traffic.

If your car has cruise control, you can save up to five per cent in petrol use when using it on open roads, according to the same researchers. Cruise control lessens accidental braking and acceleration and keeps speeds consistent, which helps save fuel.

	% of fuel saved	km of fuel saved per 500km tank
Smooth driving: new driver	5%	25km
Smooth driving: experienced driver	30%	150km
Using cruise control	5%	25km

Driving in reverse

Do you back out of your driveway every morning to go to work, then park nose-first on arrival? You may inadvertently be wasting fuel by reversing when the engine is still cold. If the engine is cold, and the fluids in the engine are also cold, friction is increased making it harder for the engine to operate at its peak thermal efficiency. Here are another couple of reasons why reversing uses more fuel than driving forward.

1. Aerodynamics: cars are designed to be aerodynamic travelling forward, so when in reverse the wind drag will be higher.
2. Increased RPMs: the car is in reverse which means it’s in a lower gear and is driving at a higher RPM so the engine has to work harder to move the vehicle. On top of that, driving backwards takes longer than driving away forward and idling uses up a lot of fuel.

Driving backwards requires the engine to work a little harder, so you use more fuel. Reversing to park when your engine is already warm, then driving out forward after your car has cooled down can potentially reduce petrol use by up to 30 per cent.

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Raising the roof racks

Roof racks are handy for transporting bulky items, but when not in use they may be consuming unnecessary fuel. Cars are designed with aerodynamics in mind, often with smooth, sloping surfaces to reduce drag, improve fuel efficiency and enhance stability.

When the normally smooth, sloping roof of a car is interrupted by bars or a frame, the aerodynamics are compromised even when they’re empty, increasing drag and making the engine work harder. Driving at urban, city speeds with an unladen roof rack can increase fuel consumption by one to two per cent. At higher speeds on freeways, roof racks can increase consumption by up to 15 per cent.

Therefore, if your roof racks are easily removeable, consider taking them off while not in use and you might save a few dollars.

	% of fuel wasted	km of fuel wasted per 500km tank
Roof racks in urban areas	2%	10km
Roof racks in high speed areas	15%	75km

Staying cool

It seems that no matter what, staying cool is going to cost you fuel.

Turning on the air-conditioner, especially in vehicles manufactured before 2018, can have an impact on petrol usage. The extra fuel used can range from 1.3 to 7.5 per cent while driving and as high as 13 per cent when idling, according to researchers for the National Academy of Science Transportation Research Board. Why? Pressing the AC button triggers a compressor attached to the car’s engine, forcing the RPMs to increase as the engine works harder to cool the cabin.

Conversely, driving with the windows down (especially at higher speeds) causes wind resistance. Remember those aerodynamics? Open windows cause more wind drag, forcing the engine to work harder which equals more fuel.

This isn’t to say you should drive sweaty and overheating. A good rule of thumb is to put your windows down while driving in urban or city areas to avoid wasting fuel idling with the air-con. Then wind the window up and crank the air-con when you’re out on the freeway to avoid aerodynamic drag.

	% of fuel wasted	km of fuel wasted per 500km tank
Aircon on while driving	1.3%	6.5km
Aircon on while idling	13%	65km

Under-inflated tyres

Tyres can be temperamental, losing up to two PSI per month. Even fluctuations in temperature can change the pressure by up to two per cent either way. This tip may be challenging to keep an eye on, but if check your tyre pressure regularly, you may save on fuel as well.

Under-inflated tyres increase vehicle drag due to more rubber against the road surface. This ‘rolling resistance’ makes the engine work harder to move the vehicle. The result: a fuel consumption increase of up to 10 per cent.

A study by the National Highway Traffic Safety Administration specifies a one per cent decrease in tyre pressure correlates to a 0.3 per cent reduction in fuel economy. So next time you get petrol, check your tyres while you’re there.

	% of fuel wasted	km of fuel wasted per 500km
Under-inflated tyres by 1% 30 PSI to 29.7 PSI	0.3%	1.5km
Under-inflated tyres by 2 PSI 30 PSI to 28 PSI	6.66%	33.3km