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With petrol and diesel prices having shot to sky-high levels, there’s never been a better time to focus on driving economically.
While you may have picked up a few tips over the years about saving money through more fuel-efficient driving, do you know how they actually help? And has anything changed as car technology evolves?
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Greg Carter, public affairs technical specialist for the AA, says: “By adopting good eco-driving techniques, a 10% fuel saving off your weekly bill is easily achievable.”
Let’s begin with a tip that many of you probably already know: being gentle with the right-hand pedal. However, the savings depend heavily on where you do it.
Nick Lyes, Policy and Standards Director at IAM Roadsmart, says: “The biggest saver from a driving point of view is driving style: smooth and gentle acceleration and braking and better anticipation of roundabouts and red lights to prevent the vehicle from stopping altogether.”
Aggressive driving – which includes speeding, rapid acceleration, and harsh braking – can raise your fuel consumption by up to 40%. So, ease back, and you might be surprised at what a difference it makes.
With 20mph now the default speed limit in built-up areas in Wales, and some other urban areas in England and Scotland, you might assume you're burning more fuel. In fact, studies show that capping urban speeds at 20mph reduces the stop-start acceleration that burns the most fuel, potentially saving you up to 10p per mile in town.
Another technique worth using involves checking out the terrain ahead. Simon Williams, head of policy at the RAC, says: “When you spot a hill coming, try to accelerate a little before you reach it, then ease off as you drive up.
“The extra momentum should be enough to minimise additional fuel consumption.”
“The extra momentum should be enough to minimise additional fuel consumption.”
Any additional load on the engine, such as using the air conditioning unit, will add to fuel consumption. Although the exact amount varies, some studies put it at 5%, while others suggest around 10%. Regardless of the exact figure, it heavily influences fuel efficiency, particularly when the car first starts and the cabin is at its hottest.
At lower speeds (typically under 40mph), simply having the windows open will help the car cool and is therefore more cost-effective than using the air-con.
At high speeds, aerodynamic drag comes into play. A classic 2013 study tested a Toyota Corolla and Ford Explorer, finding that the Toyota was less efficient at cooling the car with the windows open once it reached 80mph. However, the Ford maintained greater efficiency with the windows open over the air-conditioning unit no matter the pace. In modern, highly aerodynamic cars, it's generally accepted that closing the windows and using the air-con on the motorway is the most efficient choice.
Driving isn’t always a pleasure, and some days it’s tempting to put your foot down just to get there. But there’s a sweet spot for efficiency that hasn’t changed for most internal combustion engine (ICE) cars.
"In a conventional diesel or petrol car, you can reduce your fuel consumption by 15-20% by reducing cruising speed from 80 to 70 mph, depending on the vehicle," says Carter.
"And a further 10-15% by driving at 60 mph."
Bear in mind that most manual vehicles hit peak efficiency between 50 and 60 mph.
If you can’t drive at a constant speed, forget cruise control. It is strictly designed for large, flat roads and motorways to smooth out acceleration and deceleration. If you use cruise control anywhere other than low-traffic trunk roads, you’ll need to enable and disable it far too often to gain much efficiency – plus it will make it harder to maintain safe control of your vehicle.
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Rolling downhill or approaching a junction with the car out of gear used to be common practice, especially during historic fuel shortages. Now, it’s actively discouraged.
First, coasting doesn’t actually save any fuel. Modern fuel-injected cars automatically cut off the fuel supply when you decelerate in gear. Second, while there isn't a specific 'coasting fine', doing so reduces your control of the vehicle. If you are involved in a collision or caught coasting recklessly, you can be charged with 'driving without due care and attention', resulting in a £100 on-the-spot fine and three penalty points, potentially rising heavily if it goes to court.
“Rolling downhill out of gear actually uses more fuel, as the car will be using fuel to keep the engine running – and your control of the vehicle is reduced," says Carter.
The best practice when slowing down or driving downhill is to remain in gear but take your foot off the accelerator as early as possible.
If you only check your tyre pressures before a long journey, you need to change your habits.
Tyres lose air at a rate of up to two pounds every month – and even more in hot weather. Underinflated tyres increase rolling resistance on the road, meaning your engine has to work harder and use more fuel. So, if you’re not doing it already, check your pressures every month.
Remember, too, that if you’re carrying additional weight, such as a car full of passengers and holiday luggage, the required tyre pressure might be different. Always check your car’s handbook for the correct fully-laden pressure.
We’re all guilty of nipping out in the motor for odd errands. But if you can consolidate multiple errands into one larger round trip, you’ll noticeably improve your car’s fuel efficiency.
“Once the engine is warm, it will operate at its most efficient,” says Lyes. “Several cold starts will increase fuel consumption, even though the total mileage could be the same.”
Modern mapping software can now show you the most fuel-efficient route – taking into account fewer hills, less traffic, and more constant speeds – to make your round trip wallet-friendly. On Google Maps, simply look for the route marked with a little green leaf.
Check for local zones: Route planning can be essential to avoid surprise charges, such as tolls or the congestion charge in central London. If you have an older petrol or diesel vehicle, be aware that Scotland has now enforced Low Emission Zones (LEZs) in Aberdeen, Dundee, Edinburgh, and Glasgow, slapping non-compliant vehicles with £60 fines. London’s Ultra Low Emission Zone (ULEZ) covers all boroughs. If you're not sure, check whether your vehicle meets the standards and if necessary ensure your route planner is set to avoid these areas.
With super unleaded fuel currently costing around 12p to 14p more than normal petrol, and premium diesel around 13p to 18p more than standard diesel, is it really worth the extra expense?
"If you have a high-performance car, a premium fuel may improve driving performance and fuel efficiency and may even be recommended by the manufacturer," says Simon Williams.
"But for the everyday motorist, it’s not really going to make a difference to your vehicle’s performance, but it will obviously cost you significantly more money."
If you like the sound of the engine-cleaning additives found in premium fuel, experts suggest that just putting a tankful in a few times a year is enough to get the dirt-stripping effect, particularly for diesel engines.
Finding the cheapest fuel is essential right now. However, driving five miles out of your way to save 2p a litre is a false economy. Use free petrol cost comparison websites or apps, such as FuelFinder, PetrolPrices or the RAC’s myRAC app, to scope out the cheapest forecourts along your planned route.
One common tip for fuel-efficient driving is removing any unnecessary weight, especially from a heavily-filled boot or roof box. But do you know what effect that weight actually has on your wallet?
As a rough guide, for every additional 45kg your car carries, you’re reducing fuel economy by 2%, according to the RAC Foundation.
For a single 100-mile trip, carrying an excess 90kg might only cost you around £1 extra. However, if you lug that weight around all year, the costs quickly pile up.
Similarly, if you leave the roof rack, roof box, or bike carrier in situ when not in use, you are creating severe aerodynamic drag. At 75mph, an empty roof rack adds 16% to fuel consumption, and a roof box can add over a third, according to Energy Saving Trust figures.
That means by simply unbolting your roof box, you’ll save nearly £10 on an average motorway-based 100-mile trip – a quick win that puts cash straight back into your pocket.
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