What is the difference between China 6a and 6b?
3 Answers
The differences between China 6a and 6b are: 1. Different carbon monoxide emissions: The emission standard for carbon monoxide in China 6a is 700 milligrams per kilometer; the emission standard for carbon monoxide in China 6b is 500 milligrams per kilometer. 2. Different non-methane hydrocarbon emissions: The emission standard for non-methane hydrocarbons in China 6a is 68 milligrams per kilometer; the emission standard for non-methane hydrocarbons in China 6b is 35 milligrams per kilometer. China 6 refers to the National Sixth Stage Motor Vehicle Pollutant Emission Standards. Emission standards refer to the national motor vehicle pollutant emission standards, which regulate the content of harmful gases such as carbon monoxide, hydrocarbons, nitrogen oxides, particulate matter, and soot emitted from vehicle exhaust. They are categorized by letters as: China I, China II, China III, China IV, China V, and China VI.
I've researched extensively, and the biggest difference between China 6a and 6b lies in emission standards. China 6a serves as a transitional version, with carbon monoxide emission limits set at 700 milligrams per kilometer, while China 6b slashes it directly to 500 milligrams. The particulate matter limit also drops from 4.5mg to 3mg. The most stringent aspect is that China 6b introduces real-driving emission tests - vehicles must be equipped with instruments and driven through urban, suburban, and mountainous routes, making cheating virtually impossible. Additionally, most China 6b models come equipped with particulate filters, and have stricter requirements for fuel sulfur content. When selling China 6a inventory cars last year, salespeople kept reminding me that China 6b would be mandatory the following year, and buying now could save me twenty thousand yuan.
Last time I accompanied a friend to buy a hybrid car, I finally understood this matter. China 6a was basically a buffer period for automakers, implemented first in July 2019. China 6b is the complete standard, fully rolled out in July 2023. The most critical difference is the limit for non-methane hydrocarbons plus nitrogen oxides, where China 6b is nearly one-third stricter than 6a. China 6b vehicles must undergo PN particulate number testing and also require RDE real-world driving emissions testing. I've seen test cars with instrument boxes mounted on their roofs driving all over the city - any data falsification would mean immediate failure. Now all newly launched vehicles are China 6b compliant, with even GPF particulate filters becoming standard equipment.
