Eco-driving

eco driving tips

The great opportunity of eco-driving is that it can provide immediate fuel use and emissions benefits for all vehicle types and ages, and is not dependent on buying a new vehicle. Adopting moderate eco-driving techniques, which take into account existing engine technology can result in fuel savings and carbon dioxide reductions of around 5%-10%.

In addition to CO2, local air pollutants such as nitrogen oxides (NOx) and particulates (such as PM10) are also significantly reduced. Eco-driving can also reduce driving stress, and is proven to reduce the risk of accident to drivers and other road-users.

Many of the best practices for eco-driving are subtle, but they can add up over a year. In addition to keeping a vehicle well maintained and regularly serviced, adopting eco-driving techniques can be the most immediate and effective way to reduce fuel use and carbon dioxide emissions, whatever vehicle you drive.

Eco-driving techniques

Listed below are eight top eco-driving techniques as recommended by Next Green Car.

1. Check your tyre pressure

Under inflated tyres are not only unsafe, they also add to rolling resistance and therefore increase fuel consumption (mpg) by up to 5%. This means that keeping your tyres at the correct pressure is worth as much as a free tank of fuel per year.

To check your tyre pressure is correct, most (but not all) fuel stations have air check and refill facilities. Alternatively, invest in a tyre pressure gauge/pump for less than £10. Other ideas include switching to ‘energy-saving' tyres which, can improve fuel economy (and so reduce CO2 emissions) by up to 6%. Specialist electric vehicle tyres also being introduced to the market which according to the manufacturers, increase range by reducing the rolling resistance.

2. Remove excess weight

Any extra weight in a vehicle will increase the vehicle’s inertia requiring the engine to work harder to move it, and that effort uses fuel. While it may be convenient to leave items in your vehicle, this extra weight will reduce your car’s fuel economy and therefore increase CO2 emissions. For an average car, for each 15 kg of weight of the vehicle, fuel economy reduces by around 1%.

To reduce all unnecessary vehicle weight, try not to store items such as buggies and golf clubs in the car boot. While space-saving accessories such as roof racks, bike carriers, and roof boxes are useful when required, they add weight and increase aerodynamic ‘drag’ (so increasing fuel use), so remember to remove them when not in use.

3. Check your ‘revs’

Choosing the right gear is important to match a vehicle’s engine output to the vehicle speed and road conditions. The ‘wrong’ gear will reduce efficiency and waste energy. New eco-driving techniques demonstrate that fuel economy can be improved by ‘changing up’ to the next gear more quickly that previously recommended.

Selecting the most efficient gear can be achieved by changing up when the engine speed (as measured in ‘revolutions per minute’ or ‘rpm’) reaches a certain value. If you drive a diesel car, try changing up a gear when the rev counter reaches 2,000 rpm; for a petrol car, change up at 2,500 rpm. If you’re in an electric vehicle, try to remain in the eco or similar acceleration range.

4. Ride the ‘green wave’

Generally speaking, more energy is required to accelerate a vehicle than to maintain a steady speed. In most cars, energy is also ‘wasted’ during breaking (fuel energy used for acceleration ends up as heat during braking). It therefore pays (economically and environmentally) to avoid unnecessary accelerations, decelerations, starts and stops.

Improve your fuel economy and save money by anticipating traffic flow and keeping your car keep moving in traffic; ‘steady-and-slow’ is better than ‘stop-and-go’. When you have to slow down or to stop, decelerate smoothly by releasing the accelerator in time, leaving the car in gear. If your car has automatic start-stop, make sure its activated and you’re using it when stationary. When driving with minimum effort, you’ll be riding the ‘green wave’.

5. Reduce your top speed

At high speeds, most fuel energy is required to overcome engine friction, rolling- and wind-resistance. As friction and drag factors increase with velocity, fuel economy is drastically reduced for higher speeds. Compared to the most fuel efficient speed of around 45-50 mph (in highest gear), increasing your speed to 60 mph typically reduces fuel economy by 6%; increasing from 60 mph to 70 mph, fuel economy falls by a further 9%.

Keeping well within maximum permitted speed limits will therefore reduce CO2 emissions and save money on your petrol costs. Slowing down from 70 mph to 60 mph on a motorway will typically reduce CO2 emissions by 20 g/km, which is equivalent to a saving of around 10p per litre on fuel. You will also significantly reduce the risk of accidents to yourself and other road users.

6. Use air-con sparingly

Air-conditioning units are highly fuel thirsty and, when in use, drastically reduce a vehicle’s overall fuel economy. Although model dependent, air-con can increase fuel use, and hence CO2 emissions, by 20%-40% when engaged; other local pollutants are also increased by over 70%. It is also worth noting that the standard European test cycle (which provides official fuel economy data) is conducted with the air-con turned off.

Before you next use an air-con unit, it is worth remembering that turning it on will increase your CO2 emissions by up to 80 g/km; equivalent to an increase of around 40p on a litre of fuel. If you have to use air-con, keep it for use at higher speeds, and open windows at lower speeds.

7. Plan ahead

Consider the route you are taking and the traffic levels at the time of your journey, possibly check traffic news before you set off. If the route you are taking is an unfamiliar one, be sure to plan ahead to reduce the risk of getting lost.

8. Switch off

As mentioned above, many newer cars automatically turn off when stationary. If yours doesn’t, turn off your engine when you’ve stopped for a minute or so to save fuel. According to the Environmental Defence Fund, for every two minutes a car is idling, it uses about the same amount of fuel as would be used to travel about a mile.

Peter Thomas

Author:Peter Thomas
Date Updated:10th Mar 2015

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