In the fuel-economy of a vehicle, it is distinguished between the consumption values:
MpGh (miles per Gallon) = highway fuel economy
MpGc = city fuel economy
MpGc/h = combined fuel economy
where:
Eq. 3-31

The fuel measurement takes place indirectly over a carbon balance of the exhaust compounds (HC, CO, CO2). The following is applicable here:

Eq. 3-32

where: x = 2,424 for gasoline
x = 2,778 for diesel
HC, CO, CO2 = measured exhaust in gram per mile
From the fuel economy of each type of car assessed according to the number of units sold, the average annual consumption of a particular model from a manufacturer is determined as illustrated in the figure.
A statutory limitation of the fuel consumption is also being discussed in Europe. However, a uniform test concept does not exist yet.