1. There are some subtle differences in the appearance of Yuchai and Yudong. You can observe the designs and logos on the engine casing, radiator, air inlet and other parts to see if they match the Yuchai or Yudong brand logo.

2. There are also some differences in the brand logos of Yuchai and Yudong. You can check the logo on the engine and compare it with the official logos of Yuchai and Yudong.

3. The product models of Yuchai and Yudong are also different. You can check the model number on the engine and compare it with the model numbers on the official websites or product manuals of Yuchai and Yudong.

4. You can check the official websites, product manuals and other information of Yuchai and Yudong to understand their characteristics and differences.