Fuel Economy
The background to fuel economy testing
To maintain strict comparability of results achieved by the standard tests they cannot be fully representative of real-life driving conditions. Firstly, it is not practicable to test each individual new car; thus only one production car is tested as being representative of the model and may therefore produce a better or worse result than another similar vehicle. Secondly, there are infinite variations in driving styles and in road, car and weather conditions, all of which can have a bearing on the results achieved. For these reasons the consumption achieved on the road will not necessarily accord with the official test figure reported.
The test is outlined in Directive 93/116/EC as amended by Regulation (EC) 692/2008. There are two parts to the test: an urban and an extra-urban cycle. The cars tested have to be run-in and must have been driven for at least 1,800 miles (3,000 kilometres) before testing.
Urban Cycle
The urban test cycle is carried out in a laboratory at an ambient temperature of 20oC to 30oC on a rolling road from a cold start, i.e. the engine has not run for several hours. The cycle consists of a series of accelerations, steady speeds, decelerating and idling. Maximum speed is 31mph (50km/h), average speed 12mph (19km/h) and the distance covered is 2.5 miles (4km).
Extra-Urban Cycle
This cycle is conducted immediately following the urban cycle and consists of roughly half steady-speed driving and the remainder accelerations, decelerations, and some idling. Maximum speed is 75mph (120km/h), average speed is 39mph (63 km/h) and the distance covered is 4.3miles (7km).
Combined Fuel Consumption Figure
The combined figure presented is for the urban and extra-urban cycle together. It is therefore an average of the two parts of the test, weighted by the distances covered in each part.
Tips for saving fuel when driving
There are several ways in which you can reduce fuel consumption when driving your vehicle. These include:
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Planning ahead - choose uncongested routes
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Avoiding cold starts - drive off as soon as possible after starting the engine
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Driving smoothly and efficiently - avoid harsh acceleration and heavy braking, which can significantly increase fuel consumption
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Slowing down - driving at high speeds burns more fuel
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Using higher gears, as soon as traffic conditions allow
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Switching the engine off when you're stationary in traffic, provided it is safe to do so
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Avoiding carrying unnecessary weight – e.g. by removing roof racks when not in use
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Servicing your vehicle regularly, so that the engine runs at peak efficiency
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Making sure the tyres are inflated to the correct pressure for the vehicle and load carried
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Keeping an eye on your fuel consumption, and look out for any changes in overall fuel consumption that may indicate a fault with your vehicle
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Using air-conditioning sparingly - these systems increase fuel consumption significantly