The last six digits of a car engine number (visible on the vehicle registration certificate) typically include the engine model, production date, and a randomly assigned serial number given when the engine comes off the production line. Some may also contain a place-of-origin code (though this code is only understood by the manufacturer). The arrangement and content of engine numbers vary by manufacturer. Engines installed in passenger cars or multi-purpose passenger vehicles are required to display the professional manufacturer's name, model, and production number in accordance with regulations. To facilitate production management and usage, the national standard (GB725-82) "Rules for the Naming and Model Designation of Engine Products" provides unified regulations for engine names and model numbers. Components of a car engine number: Prefix: Includes product series code, generation symbol, and regional or enterprise code. Manufacturers may choose corresponding letters as needed, subject to approval and filing by the industry standard authority. Middle section: Composed of symbols for cylinder count, cylinder arrangement, stroke, and bore diameter. Suffix: Consists of structural and usage characteristic symbols. Tail: Distinguishing symbol. When differentiation is needed due to improvements or other reasons within the same product series, manufacturers may select appropriate symbols, with the suffix and tail separated by a "-".
