Engine Idling: How Much Fuel Are You Wasting?

The Zero MPG Problem

When your car is running but not moving, you are achieving exactly zero miles per gallon. Despite this, millions of UK drivers leave their engines idling every day-whether they are waiting outside the school gates, sitting in a drive-thru queue, or defrosting the car on a cold winter morning.

The Financial Cost

Exactly how much fuel does an idling engine consume? According to automotive engineers, a typical 2.0-litre engine consumes between 1.0 and 1.5 litres of fuel per hour of idling. If you sit idling for just 10 minutes a day (5 minutes warming up the car, 5 minutes waiting in traffic or at the shops), you are wasting roughly 60 hours of fuel a year.

At current UK prices, that 10 minutes of daily idling is costing you anywhere from £80 to £130 a year-literally burned into thin air.

The "10 Second" Rule

There is a persistent myth that starting an engine requires a massive surge of fuel, and therefore it is cheaper to leave the engine running if you are only stopping briefly. This was true for carbureted cars in the 1980s, but it is completely false for modern fuel-injected engines.

Modern engines use a minuscule amount of fuel to start. The break-even point is just 10 seconds. If you are going to be stationary for more than 10 seconds, turning your engine off and restarting it will save you fuel.

Stop-Start Technology

If your car is equipped with automatic Stop-Start technology, never disable it! It was designed specifically to combat idling losses in heavy traffic. Let the computer shut the engine down at red lights, and use FindPetrol to ensure you pay the lowest possible price when you finally do need to top up your tank.

Local prices differ far more than most drivers expect. For a worked example, see current petrol prices in Glasgow.

Cheaper fuel beats better mileage

Driving technique is worth a few percent on consumption. Choosing the right forecourt is often worth more. With more than 10p a litre between the cheapest and dearest stations in most towns, a two minute check before you set off usually saves more than a month of careful driving. We publish live prices for 2,283 UK towns - find fuel prices near me or browse prices by region.