Why is the fuel efficiency of American cars measured in MPG while Korean cars are measured in km/L?

You may have wondered about this. Many people simply know that "Korea measures per liter, and America measures per gallon," but behind that lies a much more complex difference in systems and testing methods.

First, the most noticeable difference is the unit. Korea uses km/L, which is based on how many kilometers can be traveled per liter, while America uses MPG, which stands for miles per gallon. One gallon is about 3.785 liters, and one mile is about 1.609 kilometers, so they can be converted to each other.

In simple terms, 1 km/L is about 2.35 MPG, and 1 MPG is about 0.425 km/L. Therefore, even for the same car, the numbers appear much larger in American data and smaller in Korean data. Although it is just a difference in notation, it significantly affects people's perceptions.

Next is the measuring agency. In the U.S., the Environmental Protection Agency (EPA) manages all fuel economy labels. They inform consumers by dividing it into city fuel economy, highway fuel economy, and combined fuel economy.

In Korea, the Ministry of Land, Infrastructure and Transport oversees the certification of new car fuel economy, with cooperation from the Ministry of Environment. Although it is also divided into city, highway, and combined, the calculation method for combined fuel economy differs from that of the U.S. Even though the same terms are used, the formulas differ, which can lead to actual numerical differences.

The testing methods also have interesting differences. Since 2008, the U.S. EPA has significantly changed its testing methods to reflect real driving conditions more closely. They consider factors such as cold starts, air conditioning use, and high-speed driving over 120 km/h.

As a result, even if the numbers are lower than before, they are evaluated as being closer to real-world driving. Korea used the European NEDC method in the past, which was problematic. Because it measured under overly ideal conditions, the numbers were much higher than the fuel economy experienced on actual roads.

Recently, they have adopted the international standard WLTP method. WLTP provides data that is much closer to real driving by reflecting acceleration and deceleration patterns and various speed ranges.

There are also differences in the calculation of combined fuel economy. The U.S. averages the city (55%) and highway (45%) proportions, while Korea mixes four segments: city, suburban, highway, and high-speed, based on WLTP standards.

This means that Korea's combined fuel economy has a slightly higher proportion of high-speed driving. Therefore, when comparing the same car in both countries, questions like "Huh? Why is the fuel economy different in Korea?" arise.

The label displays are also different. In the U.S., they not only show fuel economy but also provide estimated annual fuel costs and CO₂ emissions. In Korea, they display fuel economy and carbon dioxide emissions, along with ratings from 1 to 5. The reflection of fuel types is also slightly different.

The U.S. tends to provide detailed specifications for each fuel type, such as Regular, Premium, Diesel, Hybrid, and Plug-in, while Korea shows hybrid and electric vehicle fuel economy and energy consumption (km/kWh) but is not as detailed as in the U.S.

In conclusion, the U.S. adopts the MPG unit + EPA method (emphasizing realism), while Korea adopts the km/L unit + WLTP method (international standard). Therefore, it is not just a difference in units, but also in testing procedures, weights, and label display items.

As a result, even for the same car, comparing American and Korean data can yield different numbers. From a consumer's perspective, understanding this difference can reduce confusion.

"Why is it 30 MPG in America but only 12 km/L in Korea?" Don't be surprised; just remember that it's due to differences in units and systems.

Now, when looking at fuel economy when buying a car, it would be good to develop a habit of checking which country's method was used to measure it, rather than just looking at the numbers. This way, you can better gauge how much the fuel economy you will experience on actual roads may differ.

Ultimately, what matters is "how close the figures are to reality."