Fuel consumption largely depends on the car you drive, but regardless of your vehicle, there are ways to reduce fuel usage, save money, and cut pollution.

In an eco-driving trial involving 50 AA staff, participants drove normally for one week and followed eco-driving tips the next. On average, they saved 10% on fuel, with the top saver cutting fuel costs by 33%.

Maintenance

• Regular servicing ensures maximum efficiency.
• Always use the correct engine oil specification (check your car manual).
• Check tyre pressures frequently, especially before long trips – under-inflated tyres increase fuel consumption.

Before You Drive

• Reduce weight – Excess weight increases fuel usage, so remove unnecessary items.
• Minimise drag – Roof racks and boxes add drag and raise fuel consumption. Pack carefully or remove them when not in use.
• Avoid idling – Idling wastes fuel. Engines warm up faster when driving, so avoid starting the engine until you’re ready to move.
• De-ice efficiently – Scrape ice manually in winter rather than leaving the car running to warm up.
• Plan ahead – Getting lost wastes fuel. Check traffic updates before your journey.
• Combine short trips – Cold starts consume more fuel. Combine errands into one trip when possible.
• Walk or cycle – For short distances, consider walking or cycling instead of driving.

Driving Tips

• Drive smoothly – Accelerate gently and anticipate the road ahead to avoid unnecessary braking. Release the accelerator early to slow down, keeping the car in gear.
• Keep rolling – Stopping and starting uses more fuel than maintaining momentum. Approach lights or queues slowly to avoid coming to a full stop.
• Shift up sooner – Shift gears early to avoid straining the engine. Aim to change at around 2,000 rpm (diesel) or 2,500 rpm (petrol). Newer cars often have gear shift indicators for efficiency.
• Use air-con selectively – At low speeds, air conditioning increases fuel use. Open windows when driving in town and reserve air-con for higher speeds. Regular use keeps the system in good condition.
• Limit electrical use – Turn off heated rear windows, demister fans, and headlights when not needed.
• Follow speed limits – Driving faster consumes more fuel. At 70 mph, fuel use is up to 9% higher than at 60 mph, and up to 15% more than at 50 mph. Driving at 80 mph can increase fuel consumption by 25%.

Idle or Switch Off?

Avoid switching off the engine to save fuel unless:

• The engine is warm.
• You expect to remain stationary for 3 minutes or more (e.g., at a railway crossing).
• The battery is in good condition.

Cars with stop/start technology are designed for frequent engine stops, featuring:

• Enhanced battery, starter motor, and charging systems.
• Secondary batteries for sensitive electronics.
• Battery monitoring to disable stop/start if the battery is weak.
• Automatic restart when the clutch or brake is engaged.
• Systems to monitor air conditioning, engine temperature, and electrical demand.
• DPF (Diesel Particulate Filter) monitoring.
• Engine bearings designed to handle frequent starts.

Coasting

Although coasting downhill used to be a fuel-saving tactic, it is no longer recommended due to:

• Reduced control – acceleration is limited in emergencies.
• Loss of engine braking – risking overheated brakes.
• No fuel savings – Modern ECUs cut fuel flow when decelerating in gear.

How Much Can You Save?

To measure your fuel savings:

1. Check your current average fuel consumption.
2. Reset the onboard computer and track a new average.
3. Compare results over similar driving periods (e.g., weeks or months).

If you don’t have an onboard computer:

1. Fill the tank and record your mileage.
2. Log fuel purchases until you’re ready to calculate mpg.
3. Refill the tank at the same pump and record the mileage.
4. Divide the total miles driven by the litres used and multiply by 4.546 for mpg.

Example:
If you drove 1,000 miles and used 101 litres of fuel:
\( \text{MPG} = (1000 / 101) \times 4.546 = 45 \text{ mpg} \)