Safety and the law come first
Efficient driving is about reducing waste, not about taking risks to save fuel. Never brake late, hold back traffic, cut across lanes, drive below a safe speed for the conditions, or skip a safety check in order to save a little fuel. Following the rules of the road and leaving enough space is generally also the efficient approach, because it avoids sudden braking.
The habits below are general. How much any one of them saves depends on the car, the road, the weather and the journey, and some will make little difference to you. Treat them as ways to reduce waste rather than guaranteed savings.
Why driving style changes fuel use
A moving car uses energy to overcome three main things: the air pushing against it, the rolling resistance of its tyres and the effort of accelerating its weight. Every time you speed up and then brake, you turn fuel into movement and then into heat in the brakes. Smoother driving wastes less of it. The same principle applies to electric cars, where it affects range rather than fuel.
Speed
Air resistance rises steeply as speed increases, so the energy needed to maintain a high speed is considerably more than at a moderate one. For many cars, fuel use per mile is generally lowest at a moderate steady speed and gets worse at higher motorway speeds. The exact figures vary between models, so it is not useful to quote a single number.
Practical points:
- Keep to the speed limit. It is a legal and safety requirement, and staying at or below it tends to use less fuel than going over it.
- On open roads, a steady speed is usually better than repeated speeding up and slowing down. Cruise control can help on long, flat, quiet roads, though it may be less helpful on hilly routes.
- Look well ahead. Spotting a red light, a queue or a junction early lets you lift off the accelerator and coast, rather than brake hard at the last moment.
Gentle acceleration and gear use
Pulling away gently generally uses less fuel than accelerating hard. Modern engines are designed to be used sensibly, so you do not need to crawl, and being too slow can disturb traffic. Change up through the gears at a sensible point in a manual car, and avoid driving at very low revs in a high gear, which can strain the engine. Your handbook or the car’s gear indicator may offer guidance.
Many modern cars cut off fuel to the engine when you lift off the accelerator while in gear and the car is moving, so coasting in gear is generally more efficient than coasting in neutral and is safer because you keep control. Do not switch the engine off while driving or coast with the clutch down, since this reduces your control.
Tyre pressure and maintenance
Tyres that are under-inflated have more rolling resistance, which tends to increase fuel use. They also wear faster and can affect handling and braking, so this is a safety matter as well as an efficiency one.
- Use the pressures recommended by the vehicle manufacturer, which are usually given in the handbook or on a label inside the door frame or fuel flap. The figure on the tyre sidewall is a maximum, not the right setting.
- Check pressures when the tyres are cold, ideally monthly and before long trips, using a reliable gauge.
- Pressures for a heavily loaded car are sometimes different, so check what the manufacturer advises.
- Check tread depth and condition, and have problems looked at by a qualified person.
Regular servicing also helps. A well-maintained car with correct oil and clean filters runs as intended, and warning lights should never be ignored.
Weight and load
Extra weight takes energy to move, particularly in stop-start driving. Taking out items you do not need, such as heavy boxes that have lived in the boot for months, is a simple step. Do not remove anything that the car legally needs or that keeps you safe, and always secure loads properly.
Roof boxes, roof racks and bike carriers add air resistance as well as weight. If you do not use them, remove them when practical; if you do, fit them following the manufacturer’s instructions and observe roof load limits. Driving with open windows at higher speeds can also increase drag, though using air conditioning uses energy too, and the balance varies by car and conditions.
Engines, idling and short trips
Idling uses fuel while going nowhere. If you will be stationary for a longer time and it is safe and legal to do so, switching the engine off is typically better. Many newer cars have automatic stop-start systems, and they are designed for this. Some places also have rules against leaving engines running outside schools, so check local guidance.
A cold engine tends to be less efficient, so several short trips can use more fuel overall than one longer trip that covers the same errands. Combining errands, or choosing active travel for very short distances, can help, as can trying out car sharing if you only need a vehicle occasionally.
Planning the journey
Choosing a route that avoids congestion, steep hills and heavy stop-start traffic can reduce fuel use, though a much longer route may cancel the benefit. Leaving at a quieter time of day, where you have the choice, can also help. Navigation apps that show traffic can be useful, but do not use them in a way that distracts you from driving.
Keeping it in perspective
Efficient driving can reduce fuel use and often costs, but the effect is usually modest compared with decisions such as how far you travel, whether you need a car for a given trip, and the type of car you choose. Think of these habits as a low-cost way to reduce waste, and keep safe driving as the top priority.