How to reduce your car's fuel consumption: a practical guide

A car's real-world fuel use is never identical to its laboratory-tested figure. Urban traffic, hills, wind, payload and mechanical condition all make each vehicle use more or less. In general, consumption breaks down into three main areas:

• Driving style: harsh acceleration, unnecessary braking, constant speed changes and very high speeds increase fuel use.
• Vehicle condition: under-inflated tyres, non-recommended oil, a very dirty air filter or minor engine faults make the engine work harder.
• Trip conditions: short trips with a cold engine, prolonged idling, roof racks or open windows at high speed raise consumption.

Each of these factors can be tackled separately. The aim is not to apply every tip at once, but to adopt the ones that fit your daily use.

Eco-driving is internationally recognised. Official agencies such as Natural Resources Canada and the UK's Vehicle Certification Agency define it as smoother, more anticipatory and more consistent driving. Its main benefits are saving fuel, cutting emissions and improving safety because it forces the driver to read the road ahead.

1. Accelerate gently

The harder you accelerate, the more fuel the engine uses. Natural Resources Canada recommends taking about five seconds to reach 20 km/h from a standstill in city traffic. Imagine a cup of coffee on the dashboard: the goal is not to spill it.

2. Keep a steady speed

Constantly changing speed — speeding up and slowing every few seconds — increases consumption. According to Canadian official tests, varying speed between 75 and 85 km/h every 18 seconds can raise fuel use by up to 20%.

3. Anticipate traffic

Keep a safe following distance and look as far ahead as possible. If you see a red light or traffic slowing, lift off the accelerator and let the car slow using engine braking rather than stamping on the brakes. Every harsh braking wastes the momentum you have built up.

4. Avoid excessive speed

Air resistance rises sharply at high speed. Data from the Vehicle Certification Agency indicates that driving at 120 km/h typically uses about 20% more fuel than at 100 km/h in many passenger cars. Natural Resources Canada notes that most cars, vans, pickups and SUVs are most efficient between 50 and 80 km/h.

5. Coast to decelerate

When you lift the accelerator while still in gear, many modern vehicles cut fuel injection almost completely. Use this fuel cut-off to lose speed without using extra fuel. When you anticipate a stop, let the car roll to a gentle halt.

A well-maintained car uses less fuel. These checks are not complex and can be done at any workshop, or in some cases by the owner:

• Tyre pressure: the EPA says keeping tyres at the manufacturer's recommended pressure improves fuel economy by an average of 0.6% and up to 3% when under-inflation is significant. Natural Resources Canada adds that driving with tyres about 0.5 bar below the recommended pressure can increase consumption by up to 4%. Check the placard on the B-pillar, fuel filler flap or owner's manual.
• Correct oil: using the viscosity recommended by the manufacturer (for example 5W-30 when specified) can improve fuel economy by 1% to 2%, according to EPA data. A low-friction API-rated oil can help further.
• Air filter: on electronically fuel-injected engines, replacing a very dirty filter usually improves acceleration rather than fuel economy. On older carburetted vehicles, a new filter can slightly reduce consumption.
• Check-engine light: if the engine warning light stays on, visit a workshop. Even a small fault can increase fuel use and emissions.
• Wheel alignment and balancing: misaligned tyres increase rolling resistance and wear. Regular checks improve handling and consumption.

Every kilogram and every item that disturbs airflow counts. The EPA, Natural Resources Canada and the VCA agree on the following points:

• Unnecessary weight: Natural Resources Canada estimates that adding 25 kg to a mid-size car increases fuel consumption by about 1%. Empty the boot of tools, sports gear or boxes you do not use.
• Roof bars and boxes: an empty roof rack can increase motorway consumption by 1% to 5%, according to the VCA. With a roof box, the increase can reach 22% at 100 km/h and 39% at 120 km/h. Remove them when not needed.
• Open windows: at high speed, open windows increase aerodynamic drag. In town it matters little; on the motorway, forced ventilation with windows closed is preferable.
• Air conditioning: it can increase consumption by up to 20%, according to Natural Resources Canada. Use it only when needed and, if available, select recirculation to cool faster. Around town at low speeds, open windows may be more efficient; on the motorway, closed windows plus moderate air conditioning is usually better.

How you organise trips has as much impact as how you drive. Three basic principles:

Avoid cold starts

A cold engine uses more fuel. The EPA warns that several short trips from a cold start can use up to twice as much fuel as the same distance covered in one journey. Combine your errands: shopping, parcel collection, laundry and so on.

Switch off during long stops

Natural Resources Canada recommends switching the engine off if the stop exceeds 60 seconds, provided you are not in moving traffic. Many modern cars do this automatically with start-stop systems; do not disable them, because they save fuel and reduce emissions.

Plan your route

Choose routes with fewer traffic lights, less congestion and steadier speeds. Avoiding jams and unnecessary detours reduces both kilometres and stops. Check traffic apps before you leave, never while driving.

Modern vehicles include aids that, when used correctly, reduce fuel use:

• Gear-shift indicator: on manual cars, it tells you when to change up. Changing up early and keeping revs low reduces consumption.
• Eco mode: softens throttle response, makes automatic gearboxes change up earlier and reduces air-conditioning load. Useful in urban driving.
• Cruise control: on motorways with steady traffic, it keeps speed constant and prevents unconscious acceleration.
• Fuel-consumption display: many drivers use up to 15% less fuel simply by watching real-time consumption and adjusting their driving, according to Natural Resources Canada.
• Hybrids and EVs: on plug-in hybrids, keeping the battery charged lets the car use more electricity and less petrol. In electric vehicles, smooth, anticipatory driving extends range through regenerative braking.

If your car lacks these systems, there is no need to change it just for that. Conscious driving produces similar results in any vehicle.

Abnormal consumption can indicate a mechanical problem. If you notice any of these symptoms, arrange a professional inspection:

• Fuel use has risen sharply without any change in your driving style or regular route.
• The engine warning light stays on.
• You smell fuel inside the cabin or see puddles under the car.
• The car loses acceleration, emits black smoke or makes unusual noises.
• Tyres wear unevenly.

A diagnostic scan can detect faults in lambda sensors, mass airflow sensors, spark plugs or injectors that affect consumption. It is also advisable to follow the manufacturer's maintenance schedule.