How to save fuel

You can't avoid the cost of putting petrol or diesel in your car's tank - but you can minimise the damage to your wallet by saving fuel where possible. Here's how to boost your mpg...

19 November 2015
How to save fuel

The cost of filling a car up with fuel is now as significant as that of filling a supermarket trolley with the family's weekly shop.

Fuel costs are beyond the control of individual motorists, but there are plenty of ways in which you can maximise the value of every litre you put into the tank.

Drive less, spend less

The first and perhaps most obvious fuel-saving tip is to drive fewer miles. That may sound a bit pie in the sky, but the fact is that almost every motorist throws away money simply as a result of not planning journeys better.

Combine tasks and chores in one trip rather than making lots of separate ones. Optimise frequently-taken routes – especially your drive to work. Less-congested roads may add a few miles to your journey, but these routes can save you money if they help you to avoid crawling through traffic blackspots.

If you've got a sat-nav, or even a map, use it rather than driving around aimlessly in the vague hope of finding your destination.

Clear out the clutter

To move weight, your car needs energy - so the more weight you have to move, the more energy the engine will have to generate.

Don't burden your car with redundant stuff you don't need, therefore, and you'll save fuel. Carry a snow shovel in winter, but leave it in the garage in summer. If the kids aren't travelling, don't take their buggy. It's worth clearing the cabin out of clutter like half-filled drinks bottles and random plastic bags full of odds and ends, too.

If you're not using the carrying capacity of external kit like roof boxes or bike racks, take them off the car. The extra wind resistance these items create has a surprisingly profound effect on fuel consumption. So does drag from under-inflated tyres, open windows and sunroofs.

Use True MPG

The car selection process is harder than it should be because 'official' fuel consumption figures are often quite inaccurate. Real-life driving is more demanding than the EU laboratory tests which produce the official figures. You should typically expect to get 10% to 15% fewer miles from a gallon than the Government figure suggests.

That's why What Car? offers True MPG, a real-world fuel economy test that gives you a personalised average fuel consumption figure you really can expect to achieve on UK roads.

The biggest difference between our True MPG fuel economy tests and the official tests is that they're conducted on roads rather than in a laboratory. Our test starts with a thorough warm-up of the car, because engines are less efficient when they're cold.

The route begins with urban driving at an average speed of 15mph, followed by a mix of dual carriageways and motorways at an average of 60mph, and finishing with another urban loop. Our testers drive at a steady pace, avoiding heavy acceleration and braking whenever possible.

The average fuel consumption on the test route is calculated from CO2 emissions, but because traffic volume varies, we only use this economy figure as a starting point. Sensors constantly record road speed, exhaust manifold pressure, throttle position, altitude, humidity and air pressure to produce a comprehensive data set, and what can fairly be called a car's ‘true' mpg.

You can use the True MPG tool here; it'll even come up with a personalised figure, based on your most common type of journey and your driving style.

Ease off the throttle

Drive in a more fuel-efficient way. You don't need to be a professional driver to do this; the key words are ‘gentle', and ‘anticipate'. Accelerate and brake gently, changing up to a higher gear as soon as possible, but not so early that the engine is struggling at low revs. As a general guide, use 2000rpm as a typical diesel change-up point, and 2500rpm for a petrol car.

Be aware, however, that modern engines are built and tested to perform reliably at high engine speeds. Driving exclusively at low revs can build up potentially damaging residues on valves, or clog diesel particulate filters. Occasional runs up to higher revs are actually good ‘medicine' for your car's engine.

Accelerating as slowly as possible is no longer considered to be the best fuel-saving option. Apart from anything else, this technique can irritate other road users and cause safety risks.

Look far ahead and keep moving by anticipating obstacles. Ease off the throttle and keeping the car flowing rather than speeding up and braking repeatedly. Drive with a pushbike mentality: build up momentum downhill to help get you uphill, and ‘read the road ahead'.

Although it's not always practically possible, maintaining a steady 55-60mph cruise is the most fuel-efficient way to drive on motorways. Sticking to the speed limits generally is a good idea for your wallet; cruising at 70mph uses up to 25% less fuel than 80mph.

If you're going to be at a standstill for more than a minute, switch off the engine. Many modern cars come with automatic engine stop-start systems. These deliver good results if they're allowed to work, and are not being over-ridden by the driver. In a manual-gearbox car, the stop-start system will only work if you shift into neutral and lift your foot off the clutch pedal.

Switching on ‘comfort features' such as the stereo, rear demisters, lights, and air-conditioning adds to your fuel bill because the engine has to work harder to generate the power that they use.

Air-con systems are a lot more efficient than they used to be, but they're still relatively power-hungry, so don't be tempted into leaving your car's air-con switched on. In the UK, the standard heating/ventilation system in most cars is more than up to the job of handling almost all of your climate and demisting needs.

Buy oil, save fuel

Poorly-maintained engines will run less efficiently and use more fuel, so it makes sense to keep up the servicing regime. Reducing mechanical inertia and friction is now at the heart of most manufacturers' thinking. BMW's EfficientDynamics is a good example of how this kind of approach can result in great economy without compromising performance.

Dirty oil doesn't lubricate engine parts as well as clean oil. Changing it isn't a cheap exercise nowadays, but checking and replenishing the level will maintain the quality of the oil, especially if your engine is designed to consume a little oil in everyday use. It's the equivalent of a slow-motion oil change.

It's also a good idea to fill up your fuel tank from half full rather than empty, to minimise evaporation. Pump slowly to minimise the creation of vapours that get sucked back into the garage's underground storage tank (at your expense).

Play the supermarkets' game

The major supermarkets all know how much fuel bills affect us all - so they're keen to use cheaper fill-ups to get us to come back to our local store.

Watch out for offers tied in to minimum spends, or attached to loyalty cards. If you time your regular shopping correctly, you can save pence off every litre, cutting pounds off a full tank of fuel.

Should you buy a diesel car? Or would a petrol or electrified model suit you better? Our free What Fuel? tool can help you decide with four easy questions.