Eco-Driving advice to get the most out of the fuel you buy
September 10, 2008
Car choice plays a big part in the extent to which your motoring affects the environment, but whatever car you’ve got there’s a number of simple things you can do to reduce energy use (fuel consumption), CO2 emissions and pollution.
These eco-driving tips are the motoring equivalent of insulating the hot tank, fitting low energy bulbs and not leaving the tv on standby – simple, common sense tips that really will make a difference. You’ll save money on your fuel bills too.
- Regular Servicing – Get the car serviced regularly (according to the manufacturer’s schedule) to maintain engine efficiency.
- Engine oil – Make sure you use the correct specification of engine oil (refer to the handbook)
- Tyre pressures – Check tyre pressures regularly and before long journeys. Under-inflated tyres create more rolling resistance and so use more fuel. Getting tyre pressures right is important for safety too. Refer to the handbook as pressures will normally have to be increased for heavier loads.
- The benefits of Nitrogen Tyre filling:
- Improved comfort of ride
- Improved safety
- Increased fuel savings
- Improved life of tyre
Nitrogen has long been the accepted gas medium for filling aircraft tyres, racing tyres and heavy mining and construction vehicle tyres. Nitrogen is used for safety reasons and to ensure that tyres are always at a constant pressure. Compressed air, the traditional medium for inflating car tyres, contains both oxygen (21%) and nitrogen (78%).
The rubber tyre is like a membrane, through which oxygen permeates three times faster than the nitrogen. The result is that the oxygen slowly leaks out through the rubber walls, and the under-inflation leads to higher tyre wear with a consequent decrease in safety and comfort, and higher fuel costs.
Before you go
- Lose weight – Extra weight means extra fuel so if there’s stuff in the boot you don’t need on the journey take it out and leave it at home.
- Streamline – Roof racks/boxes create extra wind resistance and so increase fuel consumption. If you don’t need it take it off, if you do, pack carefully to reduce the extra drag.
- Don’t get lost – Plan unfamiliar journeys to reduce the chance of getting lost. Check the traffic news before you go.
- Combine short trips – Cold starts are inefficient so it pays to combine errands such as buying the paper, dropping-off the recycling, or collecting the kids into one trip rather than making multiple short trips.
- Consider alternatives – If it’s a short journey (a couple of miles or so) consider walking or cycling rather than taking the car – fuel consumption is worse when the engine’s cold and pollution will be greater too until the emissions control system gets up to normal temperature.
On the Way
- Leave promptly – Don’t start the engine until you’re ready to go. This avoids fuel wastage due to unnecessary idling and ensures that the engine warms up as quickly as possible.
- Easy does it – Drive smoothly, accelerate gently and read the road ahead to avoid unnecessary braking.
- Decelerate smoothly – When you have to slow down or to stop, decelerate smoothly by releasing the accelerator in time, leaving the car in gear.
- Rolling – If you can keep the car moving all the time, so much the better. Stopping then starting again uses more fuel than keeping rolling.
- Change up earlier – Change gear as soon as possible without laboring the engine – try changing up at an engine speed of around 2000 rpm in a diesel car or around 2500 rpm in a petrol car (refer to the handbook). This can make such a difference to fuel consumption that all cars in the future are likely to be fitted with Gear Shift indicators that light a lamp on the dashboard to indicate the most efficient gear change points.
- Cut down on the air-con – Air-conditioning adds to the load on the engine and so increases fuel consumption and CO2 emissions. Use it only when necessary rather than leaving it on all the time. (You should run it at least once a week throughout the year though to maintain the system in good condition.)
- Turn it off – Any electrical load increases fuel consumption, so turn off your heated rear windscreen, demister blowers and headlights, when you don’t need them.
- Stick to the limits – Drive at or within the speed limit – the faster you go the greater the fuel consumption and the greater the pollution too. According to the Department for Transport driving at 70kph uses up to 9% more fuel than at 60kph and up to 15% more than at 50kph. Cruising at 80kph can use up to 25% more fuel than at 70kph.
- Don’t be idle – If you do get caught in a queue avoid wasting fuel by turning the engine off if it looks like you could be waiting for more than Two minutes.
- Revving the engine before turning it off may reduce fuel economy.
- Warming up a vehicle on cold mornings is not required and may reduce fuel economy.
- Resting your foot on the brake pedal while driving may reduce fuel economy.
- Driving on flat terrain offers improved fuel economy as compared to driving on hilly terrain.
Coasting – does it help save fuel?
- Coasting – rolling downhill or approaching a junction with the car out of gear – is inadvisable because the driver doesn’t have full control of the vehicle, though it used to be quite a common practice to save fuel.
- You lose the ability to suddenly accelerate out of tricky situations.
- You lose engine braking which takes some of the load off the brakes on down hill stretches and helps to avoid brake fade – overheated brakes require harder pedal pressures to stop the vehicle.
- These days, coasting is still inadvisable and changes in vehicle fuel systems mean it won’t save you fuel either.
- Old car with carburetor – take your foot off the accelerator pedal with the car in gear and fuel is still drawn through into the engine. Fuel savings could be made by coasting out of gear.
- Modern car with electronic engine management – fuel and ignition systems are effectively combined and controlled by one Electronic Control Unit (ECU). Take your foot off the accelerator and the ECU cuts the fuel supply to the injectors anyway so there’s nothing to be gained by coasting.
- Modern diesel engines – these also have the ability to shut off the fuel when you take your foot off the accelerator.
How much can you save?
- The aim is to see how much you can improve on your current average fuel consumption or the ‘official’, manufacturer’s figure by following the advice above.
- If your car has an onboard computer that records fuel economy (Km/Litre) then take a note of the overall average fuel consumption you’re getting now and then see how much you can improve it by following the ‘eco-driving’ advice above.
- With no onboard computer, you’ll first need to find out the official, manufacturer quoted fuel consumption for your car. You may see three different figures quoted, ‘City’, ‘Highway’ and ‘combined’ – it’s the third, ‘combined’ figure that you want.
Measuring fuel consumption
With no onboard computer you can calculate average fuel consumption over any period by following the steps below.
- Fill the fuel tank completely and record the initial odometer reading (in kilometers).
- Do not overfill the fuel tank. The pressure in an overfilled tank may cause leakage and lead to fuel spray and fire. Allow no more than two automatic click-offs when filling.
- Always turn off the vehicle before refueling.
- Each time you fill the tank, record the amount of fuel added (in gallons or liters).
- After at least three to five tank fill-ups, fill the fuel tank and record the current odometer reading.
- Subtract your initial odometer reading from the current odometer reading.
- Follow one of the simple calculations in order to determine fuel economy:
- Calculation 1: Divide total kilometers traveled by total litre used.
- Calculation 2: Multiply liters used by 100, then divide by total kilometers traveled.
Keep a record for at least one month and record the type of driving (city or highway). This will provide an accurate estimate of the vehicle’s fuel economy under current driving conditions. Additionally, keeping records during summer and winter will show how temperature impacts fuel economy. In general, lower temperatures give lower fuel economy.
Rather than compare your new improved fuel consumption with the official combined fuel consumption you could establish a baseline average fuel consumption for your current driving style using the steps above and then another average once you’ve started applying some of the ‘eco-driving’ techniques above.
Reference: Automobile Association & Ford