With fuel prices stubbornly elevated and the end of the 5p duty discount approaching, the cost of filling up remains a significant part of motoring expenditure for most UK drivers. The good news is that how you drive and maintain your car has a meaningful effect on fuel consumption — potentially enough to make a real difference to your annual spend. Here are the measures that are backed by evidence, rather than the more speculative advice that circulates online.
The Biggest Single Factor: Speed
Aerodynamic drag increases with the square of velocity. This means the faster you drive, the disproportionately more fuel you use. The difference between cruising at 70mph and 80mph on a motorway is not 14% — it’s closer to 25% in fuel consumption terms for many vehicles, because drag increases much faster than speed.
Staying within motorway speed limits isn’t just legal compliance — it’s genuinely the most impactful single driving behaviour for fuel economy on a long journey. If you habitually cruise at 80mph, dropping to 70mph will produce a measurable improvement in fuel consumption on every motorway run.
Smooth Driving: Accelerate Gently, Anticipate Braking
Every time you accelerate hard and then brake, you’re converting fuel into kinetic energy and then dissipating that energy as heat. Smooth, progressive acceleration and early, gentle braking instead of late, hard braking uses less fuel — sometimes significantly less on urban routes.
Looking further ahead — anticipating junctions, roundabouts, and traffic flows before you reach them — naturally produces smoother driving. It’s a skill that experienced drivers develop, and it makes a measurable difference to consumption in stop-start conditions.
Engine Braking and Coasting
When you lift off the accelerator in gear, modern fuel-injected engines cut fuel delivery entirely — you’re using zero fuel while the engine slows the car. This is more fuel-efficient than coasting in neutral, where the engine returns to idle and uses a small amount of fuel to keep running. The advice to coast in neutral to save fuel is therefore largely wrong for modern cars.
When you know you’re going to stop — approaching a red light, for example — lifting off early and letting the engine brake costs nothing in fuel and delays the point at which you need to brake mechanically.
Tyre Pressures
Under-inflated tyres increase rolling resistance, which increases fuel consumption. The effect is modest but real — research suggests that tyres inflated to the correct pressure improve fuel economy by around 0.5–3% compared to significantly under-inflated tyres. Check pressures monthly and before long journeys. The correct pressures are in the handbook and often on a placard in the door sill or fuel flap.
Reduce Weight and Drag
Carrying unnecessary weight uses more fuel. A roof box, roof bars, or a bike rack left on the car when not in use adds aerodynamic drag even when empty. A roof box at motorway speeds can increase fuel consumption by 10–15%, which is more significant than most people assume. Remove accessories when not needed.
Similarly, unnecessary weight in the boot adds to fuel consumption — less dramatically than aerodynamic drag at speed, but it accumulates over many miles. Don’t use the boot as permanent storage if it’s not needed.
Air Conditioning
Air conditioning adds load to the engine and increases fuel consumption — typically by around 5–10% in urban driving, less on motorways where the engine is working harder for other reasons. At lower speeds and on short journeys, opening windows is more efficient than air conditioning. At higher speeds, the aerodynamic drag from open windows becomes the greater factor, and air conditioning becomes relatively more efficient.
The practical advice: use windows at town speeds, air conditioning at motorway speeds, and don’t leave air conditioning running when the car is stationary.
Servicing and Maintenance
A well-maintained engine is a more efficient one. Fresh engine oil of the correct grade reduces friction. A clean air filter allows proper air-fuel mixture. Correctly functioning spark plugs (on petrol engines) ensure complete combustion. A worn air filter, degraded oil, or misfiring engine can all increase consumption.
Regular servicing at the manufacturer’s recommended interval isn’t just about preventing breakdowns — it maintains the fuel efficiency the engine was designed to deliver.
Choosing Where to Buy Fuel
Supermarket fuel stations consistently offer the lowest prices per litre, and there’s no credible evidence that supermarket fuel damages engines or delivers worse performance. The fuel quality regulations in the UK apply equally to all retailers. Filling up at a motorway service station, by contrast, routinely costs 10–20p per litre more than the cheapest local option. Plan fuel stops to avoid this where possible.
Apps like Petrol Prices and GasBuddy show real-time prices at nearby stations. On a longer journey, checking before you leave and filling up locally rather than on the road can make a noticeable difference to the total cost.
What Doesn’t Work
Fuel additives that claim to improve combustion and economy have no credible evidence behind them. Aftermarket “fuel savers” — devices that attach to the fuel line or air intake claiming to improve economy — are almost universally ineffective. The interventions that work are the unglamorous ones: driving smoothly, maintaining the car, and keeping speed sensible.
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