Lower-Carbon Driving – How to Reduce the Emissions of Your Current Car
ByEven if your vehicle’s a gas-guzzler, you could probably cut its fuel usage by a tenth – and in some cases by as much as a third – by simply tweaking your driving practices. Here’s how.
Limit your speed
If you travel much on motorways, then the single most significant way to reduce the carbon footprint of your driving is to limit your speed. Most cars achieve maximum fuel efficiency at around 45-50mph. Above that level, fuel consumption rises by as much as 15% for every additional 10mph. So simply driving on the motorway at 60mph rather than 80mph can cut emissions and fuel costs by as much as a quarter.
(Of course, governments could easily force us to drive in a less polluting way by simply reducing and imposing the speed limits of main roads. This is exactly what happened in the US in 1974, when a 55mph speed limit was rolled out across the country in response to the 1973 oil crisis. To date, though, few if any governments have implemented new speed restrictions in light of climate change.)
In some cases, high speeds can be avoided at no time cost by favouring more direct routes on A-roads over longer routes on motorways.
Drive smoothly
Rapid acceleration and sudden braking will increase emissions both directly, by increasing your fuel consumption, and indirectly, by reducing the longevity of your vehicle and bringing forward the date that a new one will need to be manufactured. So it makes sense to accelerate gradually and also to take your foot off the gas as early as possible when you’re approaching a stop. Every time you press the brakes, you’re turning energy from the fuel into wasted heat.
The rules are a bit different for hybrid cars, which often operate most efficiently at 30-40mph. For many hybrids, it can increase efficiency to accelerate fairly briskly until you reach this speed range and then to employ so-called “pulse and glide” driving – basically, hovering in the optimal speed range through small accelerations and decelerations. When it’s time to slow down, brake slowly at first, then increase the pressure: this ensures that the maximum energy goes into recharging the battery versus creating unusable heat.
Whatever car you’re in, avoid pushing it too hard before changing gear. If you have a rev counter, try to shift up a gear before you reach 2500rpm in a petrol car, or 2000rpm in a diesel model.
Other ways to shave your car emissions
Keep heavy items out of the car unless you need them – you’ll typically lose a percent or two in efficiency for every extra 50kg you haul. Avoid unnecessary roof racks, too, as they increase aerodynamic resistance. Also keep an eye on tyre pressure: rolling resistance goes up and efficiency goes down by as much as 1% for every PSI (pound per square inch) below the recommended pressure range. Never over-inflate your tyres, though, as this increases the risk of accidents while doing little if anything to boost efficiency.
Another fuel drain is air conditioning, which typically cuts down a vehicles efficiency by a few percent. That said, if it’s a choice between driving with the windows down and running the A/C, there may be little difference – at least not at high speeds. That’s because wide-open windows will typically increase the car’s aerodynamic drag, and this has a higher impact as the speed increases. If outside temperatures are comfortable, try using the vents and fan but leaving the A/C off.
Finally, except when it’s required – such as in stop-and-go traffic – avoid idling. Letting the car tick over for anything more than around ten seconds will use more fuel than turning the engine off and back on. In some cars just five minutes of idling can throw half a kilo of CO2 into the air.
Consider your fuel
As well as changing your driving practices, you may also be able to improve the environmental performance of your car by switching to an alternative fuel, such as LPG for petrol cars or locally produced biodiesel for diesel cars.
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