What does National 5 and National 6 vehicles mean?

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National 5 and National 6 vehicles, the full name of which is "National Phase X Motor Vehicle Pollutant Emission Standards", refer to vehicles whose emission standards comply with the national regulations for different phases of motor vehicle pollutant emission standards. The higher the number, the later the release time, and the more stringent the energy-saving and emission reduction requirements for the vehicles. The National 6 emission standard is an upgraded version of the National 5 emission standard, with stricter limits on the emission of CO (carbon monoxide), THC (total hydrocarbons), NMHC (non-methane hydrocarbons), NOX (nitrogen oxides), PM (particulate matter mass), and the introduction of PN (particulate matter number) emission regulations compared to the National 5 standard. There are several ways to distinguish between National 5 and National 6 vehicles: 1. The National 5 emission standard is marked with a "V", while the National 6 emission standard is marked with a "Ⅵ", using Roman numerals. 2. The vehicle's nameplate indicates the complete vehicle model.