Fuel consumption measurements carried out in accordance with the standard make it possible to compare engine design solutions, the effect of vehicle weight on the efficiency of the drive unit installed in it, various types of drive systems, or different brands and models of cars. Fuel consumption test in accordance with the above-mentioned. the regulations are carried out in a laboratory on a test stand, so-called. chassis dynamometer. This test bench simulates various driving conditions.
During simulated tests on the test bench, fuel consumption is calculated on the basis of the carbon balance emitted during the exhaust gas test. The fuel consumption calculated in this way in dm3 / 100 km is required by the manufacturers in the characteristics of their vehicles.
If we buy a car, this information about fuel consumption is given in the characteristics with two numbers, np. Volkswagen Golf IV 1.4 has values 5,4/8,5 dm3 / 100 km. Means, that this model consumes a road simulated on a chassis dynamometer 5,4 dm3 / 100 km, and in the city test (also carried out in a laboratory) 8,5 dm3 / 100 km. This method of presenting fuel consumption is obligatory for car manufacturers from 1997 year.
However, we can find data specified in which fuel consumption was determined by weight and measurements were allowed at constant speeds on a test bench or on the real road. And so, for example. Skoda Fabia fuel consumption 1.4 to 5,5/9,4/6,9 dm3 / 100 km. The first number specifies steady speed driving 90 km / h in the highest gear – 5,5 dm3 / 100 km), the next one is driving at a constant speed 120 km / h in top gear – 9,4 dm3 / 100 km). The third measurement is city driving simulated on a chassis dynamometer (measurement similar to the current regulations) – 6,9 dm3 / 100 km. Many cars often use a single number in their characteristics, which is the average of the measurements taken according to the valid manufacturers of test methods.