How driving style really affects fuel economy
Of all the factors that affect how much you spend on fuel, driving style is the one you have most control over. Two identical cars driven on identical routes can return fuel economies that differ by 30% or more, purely based on how they're driven. The good news is that the changes that make the biggest difference are also the simplest.
Speed vs fuel consumption: the real curve
Most drivers assume that motorway speeds are efficient because the engine is in a high gear and cruising steadily. The reality is more nuanced. Aerodynamic drag increases with the square of speed, meaning that going from 50 to 70mph doesn't just add 40% to your drag, it nearly doubles it. Most cars reach peak fuel efficiency between 45 and 55mph. Above that, efficiency falls away quickly.
Slowing from 70mph to 60mph on a motorway run typically improves fuel economy by around 10%. On a 200-mile journey that adds less than 15 minutes to your journey time but could save over half a litre of fuel.
Smooth acceleration vs aggressive driving
Harsh acceleration (flooring the throttle from a standstill or accelerating aggressively through traffic) forces the engine to inject far more fuel than is needed for gentle progress. The difference between aggressive and smooth driving can be dramatic, particularly in urban conditions where the engine never has time to warm up and operate efficiently.
The top practical changes to make
- Anticipate the road ahead. Look 12 seconds ahead, not just the car in front. Lifting off early and coasting to a stop instead of braking late makes a huge difference in fuel use.
- Change up early. Most petrol cars are most efficient at 1,500–2,000 rpm. If the engine isn't straining, shift up. You don't need to be at high revs to accelerate smoothly.
- Gentle away from lights. Aim to reach 30mph in around 6 seconds, not slower (which keeps you in low gears longer) but not faster either. Smooth, progressive acceleration.
- Use engine braking. When you lift off the throttle in gear, most modern fuel-injected engines cut fuel delivery entirely. You're decelerating for free.
- Avoid idling. A stationary engine burns 1–3 litres per hour. If you're stopped for more than 60 seconds in a safe location, turn the engine off.
- Cold starts are expensive. A cold engine uses significantly more fuel for the first 5 minutes of driving. Combining trips and letting the car warm up while moving (not idling on the drive) keeps this cost down.
If you only make one change, make it this: look further ahead and anticipate traffic. Lifting off early and coasting instead of braking saves fuel, reduces brake wear, and is demonstrably safer. It costs nothing and delivers savings on every single journey.