How Much Money Can Eco-Driving Save?
Driving more smoothly typically cuts fuel use by 10% to 15% - around £150 to £220 a year for an average driver. At 161.2p a litre, someone covering 8,000 miles at 40mpg spends about £1,464 on fuel. The savings come from a handful of specific habits, and some of the advice you will read elsewhere is worth almost nothing.
What each habit is actually worth
| Change | Typical saving | Per year |
|---|---|---|
| Smoother acceleration and braking | 10-15% | £146 - £220 |
| 70mph instead of 80mph | 10-15% on motorway miles | up to £150 |
| Correct tyre pressure | up to 6% | £88 |
| Removing a roof box when unused | 10-20% at speed | varies |
| Removing 50kg of unnecessary weight | 1-2% | £15 - £29 |
| Filling at a station 10p cheaper | 6% | £88 |
The three that matter most
Anticipate instead of reacting
Every time you brake, you convert fuel you have already burned into heat. Looking further ahead, easing off early and rolling towards a queue rather than accelerating up to it and stopping is the single biggest change available. This is where most of the 10% to 15% comes from.
Slow down on the motorway
Aerodynamic drag rises with the square of speed, so the fuel needed to overcome it rises steeply. The Energy Saving Trust and the AA both put the difference between 70mph and 80mph at roughly 10% to 15%. On a 200-mile motorway run at 40mpg that is around £4 - and about eight minutes saved.
Change up earlier
Engines are most efficient at moderate revs under light load. Shifting up at around 2,000rpm in a diesel or 2,500rpm in a petrol, rather than revving each gear out, makes a measurable difference in town.
What barely matters
- Turning off air conditioning on the motorway. At speed, opening the windows instead creates enough drag to cancel the benefit. In slow town traffic, air conditioning does cost a few percent.
- Coasting in neutral. Modern injection systems cut fuel entirely when you lift off in gear, so coasting in neutral can use more. It also reduces control, and is poor practice.
- Removing the spare wheel. Around 15kg on a 1,400kg car. The saving is a fraction of a percent and you will regret it at the roadside.
- Filling up in the morning. The theory is that cold fuel is denser. Underground tanks barely change temperature, and the effect is far smaller than a 1p price difference.
Idling and stop-start
A modern engine uses very little fuel at idle, but it is not nothing - roughly 0.5 to 0.7 litres an hour for a typical petrol engine. Sitting for two minutes at a level crossing costs about 2p. Not dramatic, but restarting a warm engine uses less than idling beyond about ten seconds, which is why stop-start systems exist.
The exception is a cold engine. Do not idle to warm up - modern engines warm faster under gentle load, and idling simply wastes fuel.
The saving that needs no skill
Improving your economy by 10% takes sustained change in how you drive. Filling at a station 10p cheaper saves about 6% of your fuel bill and takes thirty seconds. The gap between the cheapest and dearest forecourt in most towns is 8p to 12p a litre.
Do both. Check prices on findpetrol, work out your own numbers with the fuel cost calculator, or see how to find cheaper fuel near you.
Frequently asked questions
Is 10-15% realistic, or a best case?
It is achievable for most drivers who currently accelerate briskly and brake late, and it is the range quoted by the Energy Saving Trust and motoring organisations. A driver who is already smooth will see less, because the gain is already banked.
Does eco mode do it for me?
Partly. Eco modes soften throttle response and change shift points, which helps. They cannot anticipate traffic, which is where most of the saving lives.
Do I need to drive slowly to save fuel?
No - smoothly, which is different. Steady progress at the limit uses less than repeatedly accelerating and braking at lower average speeds. The exception is motorway speed, where the drag penalty is real.
How do I know if it is working?
Track mpg over several tanks rather than trusting the trip computer over one journey. Fill completely, note the mileage, refill completely, divide miles by litres and multiply by 4.546.
Find the cheapest fuel near you
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