Early Automobile Era: In the early 20th century, when automobiles first became widely available, fuel economy was rarely a consideration. With gasoline being relatively inexpensive and environmental concerns minimal, manufacturers focused on power and comfort rather than efficiency. Nevertheless, the concept of miles per gallon emerged as a practical way to express how far one could travel on a tank of fuel.

The Oil Crises: The 1973 and 1979 oil crises dramatically changed attitudes toward fuel consumption. As gasoline prices soared and supplies dwindled, fuel economy suddenly became a primary concern for consumers and regulators alike. This period saw the first major government fuel economy standards and a shift in consumer preferences toward smaller, more efficient vehicles.

Standardization of Measurements: Throughout the 1970s and 1980s, governments began standardizing how fuel economy was measured and reported. The United States established the Corporate Average Fuel Economy (CAFE) standards in 1975, while European countries gradually adopted the liter per 100 kilometers standard, which became formalized in EU directives.

Environmental Awareness: From the 1990s onward, fuel consumption metrics became increasingly tied to environmental concerns, particularly carbon dioxide emissions. Many countries began reporting CO₂ emissions alongside traditional fuel economy measures, highlighting the environmental impact of vehicle choices. The European Union's g/km CO₂ rating is a direct extension of this trend.

Electric and Alternative Fuels: The 21st century has seen a revolution in vehicle power sources, necessitating new units for comparing efficiency. The miles per gallon equivalent (MPGe) and kilowatt-hours per 100 kilometers (kWh/100km) have emerged as ways to compare electric vehicles with traditional combustion engines, while various units attempt to standardize the efficiency of hydrogen, natural gas, and biofuel vehicles.