Why is the car god’s surname Chen?

Because his father’s surname was Chen, he was given the surname Chen Xing.

The leader of the ancient Chinese tribal alliance, the leader of the Chinese nation in ancient China, the head of the Five Emperors, revered as the "first ancestor of humanities" in China, and the great ancestor of the Chinese nation, because he invented Cars (called Xuanyuan in ancient times) have brought great convenience to people's travel and production, so they are revered as Emperor Xuanyuan and are regarded among the people as the God of Cars, the patron saint of car dealers' safety.