Car Manufacturer’s Fuel Consumption Figures
Many drivers make their choice of vehicles based on the manufacturer’s figures for FC Fuel Consumption and drivers get very disappointed by the real world FC. The fact is, car manufacturers get their FC figures based on laboratory tests to achieve consistent standards for car manufacturers. What this means is that these cars are never, never driven on the roads.
(NB. These tests are conducted without the aircondition switch on which will typically improve FC by 5-10%)
Taken from http://www.fuelsaver.govt.nz/explain.html
About the tests
New vehicle testing is carried out by independent test organisations or by the manufacturers at their own test facilities. The test results are normally part of the vehicle’s official certification in the country in which it is sold.2
Standard tests are not fully representative of real life driving conditions because:
- It is not practical to test every new car. A typical car, of every model from each production run, is chosen for testing.
- Variations in driving styles and in road, car and weather conditions can significantly influence the results achieved.
While you may not have much control over some factors (such as traffic conditions), you do have control over others (such as how you drive and how well your car is maintained). You will find tips on how to minimise fuel consumption on the Habits page.
The tests are carried out on new cars. Some deterioration of fuel consumption occurs to vehicles as they age, depending on how much they are used and maintained. As a guide, an older vehicle will consume more fuel than an equivalent new vehicle.
The European test method
There are two parts to the European fuel consumption test, an urban and an extra-urban cycle. The cars tested have to be run-in; that means they must have been driven for at least 3,000 km before testing.
Urban cycle
The urban test cycle is carried out in a laboratory at an ambient temperature of 20�C to 30�C (whereas Singapore’s ambient temperature is about 35�C) on a rolling road (measuring rollers) from a cold start; ie, the engine has not run for several hours. The cycle consists of a series of accelerations, steady-speed driving, decelerating and idling. The maximum speed is 50 km/h, the average speed is 19 km/h and the distance covered is four km. The urban cycle is repeated four times.
Extra-urban cycle
This cycle is conducted immediately after the urban cycle, and consists of about half steady-speed driving and the rest accelerations, decelerations and some idling. The maximum speed is 120 km/h, average speed is 63 km/h and the distance covered is seven km.
Combined fuel consumption figure
The results of the urban and extra-urban cycles are combined and presented as the final figure. This is arrived at by averaging the two parts of the test and weighting them by the distances covered in each part.
The European test is illustrated on the chart below.
The Japanese test method
The Japanese 10-15 mode test drive cycle is made up of two separate drive cycles. The 10 mode drive cycle is a low speed urban drive cycle, while the 15 mode cycle is a higher speed extra-urban cycle. The two cycles are combined form the 10-15 mode cycle. As with the European test, it is carried out on a dynamometer under strictly controlled conditions.
10 Mode (urban) cycle
This cycle represents low speed driving in a congested city environment. It is 135 seconds long and consists of a series of accelerations and decelerations. The maximum speed is 40km/h, while the average speed is 17.7 km/h.
15 Mode (extra-urban) cycle
This cycle represents higher speed driving in an open road environment. It is 231 seconds long and consists of a series of accelerations and decelerations at higher speeds than the 10 mode cycle. The maximum speed is 70 km/hr, while the average speed is 33.88 km/hr.
10-15 Mode (combined) cycle
This cycle starts with an initial 15 mode cycle to warm the engine up (with no emissions sample collected), followed by a short idle period. The 10 mode cycle is then repeated three times and is followed by a single 15 mode cycle. The total fuel consumption is measured using the emissions collected during the three 10 mode and one 15 mode cycles.
The Japanese test is illustrated on the chart below.
One of the best ways to get information about the real world FC is to contact the forumers at various car clubs as well as driver compiled figures at websites such as www.oneshift.com (user contributed figures at each car model selection) or, your good friend.
See also http://www.fueleconomy.gov/feg/how_tested.shtml
