What do China V and China VI mean?

[StJoseph]

China V refers to the National Fifth Stage Emission Standards for motor vehicle pollutants; China VI refers to the National Sixth Stage Emission Standards for motor vehicle pollutants. The emission control level of China V standards is equivalent to the European Fifth Stage Emission Standards currently in implementation. The China VI emission standards improve upon China V by 40% to 50%, reaching a level comparable to U.S. standards, making it one of the most stringent emission standards globally. Automobile emission standards regulate the content of harmful gases emitted from vehicle exhaust, including carbon monoxide, hydrocarbons, nitrogen oxides, particulate matter, and soot. Compared to China V fuel, China VI fuel can reduce particulate matter emissions by up to 10%, significantly lowering the pollutant content in vehicle exhaust emissions.