Fuel is one of the few household costs where your own behaviour, not a tariff or a supplier, sets a big part of the bill. You cannot change the pump price, but how you drive, how the car is loaded and whether you make the trip at all decide how much you burn. This page is the overview. It separates the changes that genuinely save fuel from the ones that barely register, and links to the deeper guides on hypermiling, electric cars and keeping a car cool in summer.
The short answer. The car you drive sets the baseline, but how you drive it is worth nearly as much. Smooth acceleration, reading the road, sensible motorway speeds and properly inflated tyres can cut a heavy-footed driver's fuel use by 10 to 20 percent. The biggest lever of all is driving less: a shared, cycled or skipped journey beats any efficiency trick. Switching to an electric car changes the maths entirely, with home charging costing a fraction of petrol per mile.
How you drive is worth real money
Two people in identical cars can differ by 20 percent or more in fuel use, and the difference is almost entirely in the right foot. Hard acceleration and late braking pour fuel away, because every burst of speed you brake off again was paid for in petrol. Reading the road ahead, easing off early and holding a steady pace use far less.
On the motorway, speed is the big one. Aerodynamic drag rises with the square of speed, so the engine works much harder at 80mph than at 70mph, and harder still above that. As a rough guide, dropping from 80mph to 70mph can cut motorway fuel use by around 10 to 15 percent, and 70mph to 60mph saves a similar slice again. Sitting a few miles per hour below the limit on a long run makes a measurable dent in the bill while adding only a couple of minutes to the journey. None of this means crawling. It means driving smoothly rather than in bursts.
Using the highest gear that the engine is happy in keeps the revs down, which a modern engine repays in lower fuel use, and a gentle right foot on the way up to speed avoids the heavy fuel use of hard acceleration. The full technique, including coasting up to red lights and reading traffic flow, is in our hypermiling guide.
Check the cheap, easy things
A few minutes of maintenance saves fuel month after month, and most of it is free.
- Tyre pressures. Under-inflated tyres increase rolling resistance, quietly costing fuel and tyre life. Check them monthly against the figure in the door jamb or handbook, and adjust up a little for a heavy load.
- Clear the boot. Carrying weight you do not need costs energy to haul around. Take out the bag of sand, the old paint tins and anything else living in there permanently.
- Lose the roof box and racks. An empty roof box or bike rack adds surprising drag at speed. Take it off when it is not in use; the fuel penalty of leaving it on for months is real.
A clogged air filter, dragging brakes or a misfiring engine all waste fuel too, so a car that is serviced on schedule runs more economically than one that is neglected. Sticking to the right grade of engine oil helps as well, since a thicker oil than the engine was designed for adds drag when cold.
These are not glamorous, but they cost nothing or next to nothing and stack up. They are the motoring equivalent of draught-proofing a house: small, dull, repaid every day.
Idling and short cold trips
An idling engine does zero miles to the gallon, so switch off in long waits at level crossings, in queues or while waiting to collect someone. Modern stop-start does this automatically, but for older cars it is worth doing by hand once you are stationary for more than a minute.
Short cold journeys are the least efficient miles a car does. A cold engine runs rich and the catalytic converter is not up to temperature, so the first mile or two burns far more per mile than a warm engine on the open road. Combining errands into one trip, so the engine warms once rather than three times, saves more than it seems. The very shortest hops are often quicker to walk or cycle, and that saves the lot.
Petrol versus electric: the running-cost gap
If you are weighing a change of car, the running-cost difference between petrol and electric is large, and it is mostly about the price of the energy. Charging an EV at home on a standard tariff costs a fraction of the equivalent petrol per mile, and a cheap overnight rate widens the gap further. The table shows a rough per-mile comparison.
| Car and energy | Efficiency | Cost per mile |
|---|---|---|
| Petrol at £1.40 per litre, 45 mpg | 45 mpg | ~14p |
| EV, home charge at standard rate | 3.5 miles per kWh | ~7.5p |
| EV, home charge on a cheap night rate (7p) | 3.5 miles per kWh | ~2p |
| EV, public rapid charger (~75p per kWh) | 3.5 miles per kWh | ~21p |
EV home rate uses 26.11p per kWh electricity, Ofgem cap July to September 2026. Petrol and rapid-charge prices vary by location and date. Worked examples; check your own figures.
The lesson is that an EV is cheapest when charged at home, especially overnight, and dearest on public rapid chargers. Our guides on EV running cost versus petrol, home charging cost and home versus public charging work through the detail, and EV electricity tariffs explained covers the cheap-rate side.
Summer: cooling the car costs fuel too
How you cool the car in hot weather plays into the bill. Air conditioning draws power from the engine and adds a few percent to fuel use, while open windows add drag, especially at speed. The rough rule is windows at low town speeds and air conditioning on the motorway, where the drag from open windows outweighs the compressor.
For an electric car, the same cooling draws from the battery and trims your range, more so in very hot conditions. Our guide to keeping your car cool and fuel economy weighs the options, and EV drivers should also see EV range in hot weather.
The honest limit, and the biggest lever
Driving habits trim a useful slice off a fuel bill, commonly into the low tens of percent for a heavy-footed driver who reforms. That is worth having, and it is free. But none of it rivals the saving from simply driving less.
A journey shared with a colleague halves its cost at a stroke. A short trip cycled or walked costs nothing in fuel and something in health gain. A trip not made at all, by batching errands or working from home, is the cheapest mile there is. Our home working energy cost guide weighs the household-energy side of skipping the commute.
So the order is: drive the trips you must make smoothly and in a well-maintained car, then question whether each trip needs making by car at all. For the deep dives, start with hypermiling for technique, the EV versus petrol comparison if you are thinking of switching, and plug-in hybrid running cost if you want a halfway step.