Core Viewpoint - The domestic internal combustion engine market showed strong annual performance in 2025, with total sales reaching 53.81 million units, a year-on-year increase of 12.76%, marking the highest sales since 2018. However, December sales experienced a slight decline due to a weak terminal market and slower supply pace [1]. Group 1: Internal Combustion Engine Sales - In December 2025, internal combustion engine sales were 4.7454 million units, a month-on-month decrease of 1.97% but a year-on-year increase of 0.98% [1]. - For the entire year of 2025, total internal combustion engine sales reached 53.81 million units, reflecting a year-on-year growth of 12.76% [1]. Group 2: Diesel Engine Sales - In December 2025, diesel engine sales were 456,300 units, with a month-on-month increase of 2.75% and a year-on-year increase of 11.62%. The total sales for the year reached 5.126 million units, up 6.8% year-on-year [4][3]. - The multi-cylinder diesel engine market also performed well, with December sales of 360,000 units, a month-on-month increase of 1.41% and a year-on-year increase of 12%. Total sales for the year reached 4.1317 million units, a year-on-year increase of 7.35% [4]. Group 3: Market Performance of Key Companies - Weichai maintained its leading position in the multi-cylinder diesel engine market with total sales of 807,300 units in 2025, achieving a year-on-year growth of 8.58% and a market share of 19.54% [8]. - Yuchai ranked second with total sales of 549,100 units, a year-on-year increase of 23.17%, and a market share of 13.29% [8]. - Yunnei Power ranked third with sales of 353,700 units, a year-on-year increase of 4.65%, holding a market share of 8.56% [8]. - In December, Weichai sold 80,500 units, achieving a month-on-month growth of 2.82%, while Yuchai and Yunnei Power sold 34,300 and 33,500 units, respectively [6]. Group 4: Strategic Partnerships - Yunnei Power and SF Express established a comprehensive strategic partnership focusing on intelligent delivery robots, with SF Express prioritizing the procurement of vehicles equipped with Yunnei Power engines [7].