- Simple driving techniques to save fuel
- What to check on your car to avoid wasting energy
- Why are claimed MPG figures hard to reach?
Achieving official fuel economy figures is often challenging – and increased scrutiny over emissions cheating and changes to the test programme have highlighted the gap between claimed and real-world costs for motorists.
Our own long term car reviews show many cars returning less than 75% of their claimed figures, with some as low as 60% - even when driven carefully.
How can you get better economy, then? There are a few small changes you can make right now, to both your car and your driving habits, that could improve the figures and get more miles per gallon. Here are our top tips for eco-friendly driving.
Official mpg figures versus real-world driving
Until recently, the standard fuel economy tests were part of a programme called the New European Driving Cycle or NEDC, which dated back to 1970. Undertaken in laboratory conditions, on a rolling road, the predetermined 'drive' specified the time taken to reach set speeds and which gears were used.
Over the time NEDC testing applied, the size and power outputs of cars changed dramatically – with average 0-62mph times dropping from 13 seconds to 9.0 seconds. In-car technology changed substantially too; and despite updates in 1997, it's clear the assumptions made for testing and some manufacturers 'gaming' the system through gearing and engine mapping often gave unrealistic results.
A global scheme to make testing more realistic and to harmonise emissions testing around the world is now in place – World Light Testing Programme or WLTP. This also includes real-world testing, and in theory will reveal figures that are closer to what drivers can expect for both economy and emissions.
Regardless of the tests used to get your car's official figures, there are several things you can do to get the best economy from your car.
Change your driving style for economy
Speed affects fuel economy significantly; typically the faster you go, the more fuel you'll use. Reducing speed generally reduces the amount of fuel needed.
How quickly you accelerate, or recover speed after hard braking, has a greater effect and is easier to influence regardless of road conditions and car performance. Anticipating the conditions ahead, and making small, progressive changes rather than abrupt reactions can yield the largest gains in economy without affecting your average speed and journey time.
Slowing down early when approaching red lights or slower traffic can help you avoid the need to stop – and subsequently pull away from standstill.
Most manual transmission cars now include a shift indicator, and changing gear when suggested will give optimum economy. Automatic cars may feature an economy mode, but all will respond well to smaller inputs on the accelerator; rather than aiming to reach the speed limit rapidly. Allowing the car to naturally build pace smoothly with a gentle touch of the pedal will cost little time and save money.
If your car is equipped with cylinder deactivation – where some of the engine cylinders shut down when driven gently - learn when it activates in each gear and try to increase the amount of time spent cruising at those speeds. Over busy routes it's likely your average speed won't be affected, but consumption will be significantly reduced.
On country roads, looking far ahead for congestion and hazards and slowing well ahead of time, planning engine braking ahead of turns and avoiding aggressive cornering – where stability programs may apply the brakes rapidly to keep the car stable – can also save some fuel.
Once your driving style is adjusted for the best possible economy, it's time to look at the car itself. Do you have a roof rack or bike rack fitted when not in use? Wind resistance from bulky accessories can reduce economy by 3-5mpg, as well as increasing wind noise. Roof boxes may look aerodynamic, but they're still increasing the surface area being pushed through the air.
Open windows and sunroofs also increase fuel consumption. You can fit wind deflectors to reduce buffeting and drag, or where fitted, use air conditioning instead – though that also has a penalty.
Ensuring your tyres are correctly inflated – check your car's handbook to find the right pressures to use - and in good condition, tracking is correct after encountering kerbs and potholes, and brakes are well maintained completes the list of things you can do without spending a significant amount.
It's also possible to fit low rolling resistance tyres, often found on high-economy models from the factory. New tyres should show an A to G fuel economy rating. Look for A-rated tyres for the least resistance.
Powering the gadgets
Cars consume energy in many ways – and for the modern vehicle there are many additional drains on your engine's output. Top of the list is air conditioning, which on many cars can cost more than 3mpg to use. Even with intelligent management and eco modes, to cool the car takes a lot of power; if you can tolerate the temperature turn it off – though, on colder days it does help with demisting the car.
Older cars can also consume a lot of power to run lights and accessories – more modern vehicles use lower wattage bulbs and LEDs. Nevertheless, heated seats, fast chargers for phones and accessories, and high-end media systems all take power to run. For best economy, keep your car's specification and your accessories simple.
Some gadgets will actually help you save fuel. If you car has stop-start technology, switch it on and use it. One of the greatest hidden costs of motoring is the time spent at a standstill in traffic with the engine still running, particularly in higher capacity models.
Third-party route planners like Waze or Google Maps will probably save you more fuel than all of the techniques above - with live traffic reports and dynamic routing to avoid congestion. Built-in navigation will usually offer a most economical route option, too.
Can a production car meet the claimed economy figures?
In most cases, real-world conditions mean you're unlikely to see the claimed figures over the lifetime of the car. Careful driving can often get you close to the claimed combined figure, however; check our long term tests to see which cars come close to meeting their advertised figures.
Regardless of actual consumption, the published figures still provide a useful comparison between models for buyers, and some might argue that the idealistic claims benefit drivers with reduced emissions-based taxation; as real-world figures are released, many cars are moving into higher brackets.