12 Proven Ways to Improve Your Car's Fuel Efficiency

What the Evidence Actually Shows

Fuel efficiency advice ranges from the genuinely useful to the completely ineffective. The tips below are grounded in research from the US Department of Energy, the RAC Foundation, the Transport Research Laboratory, and the Society of Automotive Engineers. Each one has a measurable, documented impact. The myths at the end have been tested and debunked.

The 12 Techniques That Work

1. Keep Tyre Pressure at the Correct Level

Under-inflated tyres deform more as they roll, increasing rolling resistance and forcing the engine to work harder. SAE research shows that tyres under-inflated by 8 PSI increase fuel consumption by around 3%. Multiply that across all four tyres and the effect is meaningful. Check pressures monthly using a gauge — the figure on the tyre wall is the maximum pressure, not the recommended one. The correct pressures are in your car's manual or on the sticker inside the driver's door frame.

2. Smooth Acceleration and Braking

Harsh acceleration burns fuel rapidly, and then harsh braking converts all that kinetic energy to heat — wasted. Anticipating traffic flow and coasting to a stop rather than braking at the last moment can reduce fuel consumption by 10–15% in urban driving, according to RAC Foundation research on eco-driving. The mental model is simple: every time you brake hard, you are throwing away fuel you already burned.

3. Observe the Speed Limit — Especially on Motorways

Aerodynamic drag increases with the square of speed. At 60 mph, drag is already the dominant force acting against your car. At 70 mph, consumption is roughly 9% higher than at 60 mph. At 80 mph, it's around 25% higher. The Transport Research Laboratory found that driving at 70 mph instead of 80 mph on a motorway saves approximately 25% in fuel costs for that stretch of road. This is the single highest-impact change most motorway drivers can make.

4. Use Air Conditioning Strategically

Air conditioning puts a direct mechanical load on the engine through the compressor and typically increases fuel consumption by 5–10% during use. At low speeds in urban traffic, opening windows is more efficient. At motorway speeds above 60 mph, open windows create aerodynamic drag that can exceed the fuel cost of air conditioning — so use AC on the motorway and windows in town. Parking in shade reduces cabin temperature and lowers the initial cooling load.

5. Reduce Unnecessary Weight

Every additional 100 lbs (45 kg) of weight reduces fuel economy by approximately 1–2%, according to US Department of Energy data. This effect is most pronounced in smaller cars with less powerful engines. Clear out the boot — a bag of golf clubs, a box of tools, or heavy winter equipment left in the car year-round is a constant, invisible fuel tax. The effect is small per item but accumulates over tens of thousands of miles.

6. Don't Warm Up a Modern Engine at Idle

The advice to let your engine warm up for several minutes before driving came from an era of carburettors and older engine management systems. Modern fuel-injected engines warm up faster when driven gently than when idling. Extended idling burns fuel without moving you anywhere and can actually increase engine wear in modern engines by washing oil off cylinder walls. The correct approach: start the engine and drive immediately, but keep revs low for the first mile or two.

7. Use Cruise Control on Motorways

Most drivers unconsciously vary their speed by 2–5 mph continuously on motorways. This constant acceleration and deceleration burns more fuel than maintaining a perfectly steady speed. Cruise control eliminates this variation and consistently returns better fuel economy on flat motorway sections. It is less effective on hilly routes, where some adaptive cruise systems will needlessly accelerate downhill — in those cases, manual speed control on descents may be preferable.

8. Plan Routes to Avoid Traffic

Idling in traffic is among the worst uses of fuel — you're burning petrol to go nowhere, and repeatedly accelerating from standstill is the most fuel-intensive type of driving. Leaving 15 minutes earlier (or later) to avoid peak congestion, using live traffic apps like Waze or Google Maps to find lower-delay routes, or working from home on high-congestion days can each deliver fuel savings that dwarf any driving technique.

9. Service Your Engine Regularly

A clogged air filter restricts airflow into the engine, forcing it to work harder and run richer fuel mixtures. Old spark plugs misfire, wasting fuel that doesn't combust properly. Degraded engine oil increases internal friction. Regular servicing — at manufacturer-recommended intervals — keeps all these systems operating efficiently. A car that is significantly overdue for a service may be running 5–10% below optimal fuel efficiency without any obvious drivability symptoms.

10. Use the Correct Fuel Grade

If your car is designed to run on standard unleaded (95 RON in the UK, 87 octane in the US), there is no measurable fuel economy benefit from using premium (97–99 RON, or 91–93 octane). Premium fuel has a higher octane rating — which prevents knock in high-compression engines — but does not provide more energy or better combustion in engines not designed to use it. Save the premium price for cars that specifically require it. However, if your manufacturer specifies premium, using standard fuel can reduce efficiency and may cause knock-related damage over time.

11. Remove Roof Racks and Roof Boxes When Not in Use

An empty roof rack increases aerodynamic drag and typically reduces fuel economy by 5–10% at motorway speeds. A loaded roof box increases drag further — by 15–25% in some configurations. Many drivers fit a roof box for one holiday and then leave it on the car for months. That decision costs real money: at 70 mph, an empty roof rack on a car doing 15,000 motorway miles per year could add £80–£150 to annual fuel costs.

12. Combine Short Trips

A cold engine running below optimal temperature uses significantly more fuel than a warm one. In the first mile of a cold start, fuel consumption can be 20–50% higher than normal as the engine management system runs a richer fuel mixture to warm up quickly. Multiple short trips — each starting from cold — multiply this penalty. Combining errands into a single trip, or sequencing them so you don't return home between stops, meaningfully reduces cold-start fuel waste over the course of a week.

The Myths That Don't Work

Premium fuel in a standard engine — no measurable benefit. The engine cannot use the higher octane rating and burns the same amount of fuel for the same energy output.

Fuel additives and injector cleaners — Consumer Reports and independent testers have consistently found these deliver no measurable fuel economy improvement in well-maintained engines. Some products may help a neglected engine return to normal, but they cannot improve efficiency beyond the manufacturer's design.

Drafting lorries — tailgating large vehicles to reduce aerodynamic drag is technically effective at reducing drag, but the safety risks are severe and the following distance required to see any benefit (under 30 metres) is illegal and dangerous at motorway speeds. This is not a strategy — it's a hazard.

What Realistic Savings Look Like

Combining the above techniques — correct tyre pressure, smooth driving, moderate speeds, removing unnecessary weight, and combining trips — realistically delivers 10–20% lower fuel consumption for most drivers. At UK fuel prices in 2025, that represents a saving of £150–£400 per year for an average annual mileage of 7,400 miles. None of these changes require spending money. Most require only attention and small habit adjustments.