when stated in a vehicle brochure that the fuel consumption /100 KM is a certain value,is that at part load or full load or average between them?
Actually in the laboratory specific fuel consumption is measured in kg/kW h. It is always higher at low and very high engine speeds. There is an economical speed in between at which fuel consumption is called economical. This engine speed may be corresponding to a cruising speed in the range between 90 to 100 kilometers per hour for most vehicles. But at low or very high vehicle speed consumption will definitely become excessive.
Fuel consumption values in the brochures are normally determined by experiment. (Not on the road but on a roller dynamometer to make the experiment repeatable.)
Normally there should be an indication as to which test was applied (e.g. 'NEFZ' - Neue Europäischer FahrZyklus/'NEDC' - New European Drive Cycle or alike). You should be able to locate the meaning of some "cryptical" acronyms in wikipedia.
These consumption numbers are near the absolute minimum consumption - and way from practical consumption. There is a number of reasons: temperature, YOUR driving cycle (that may not fit the idealized standard cycle), fuel quality, tire pressure etc. pp.
The drive cycles used until recently are to some extend 'typical', but to some extend also defined as not to get high consumption numbers. Better cycle definitions are under work, but not yet implemented.
Regards
There are different test procedures, and any computation uses parameters derived from some experimentation.
Fuel quality, altitude, temperature, vehicle setting, are among many factors
For heavy duty vehicles, trucks and busses, a combined test and simulation based procedure is being developed. The idea is to test critical subsystems, like engine and transmission in test rigs, and to test air drag and rolling resistance in specialized test procedures and then to simulate the full vehicle fuel consumption in realistic driving scenarios. The benefit with the combined testing and simulation is that many different variants can be evaluated at lower cost. The accurcay of the predicited fuel consumption is also expected to be better and much closer to real driving figures compared to current procedures for passenger cars.
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