system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Why do cars have displacements of, for example 2,997cc instead of just exactly 3,000cc?
gpt
There are several reasons.   The displacement of the motor is simply the swept volume of the cylinders.  The designer of the engine builds to a certain performance and size target, as well as maximize the use of off-the-shelf, common parts (like bearings and piston rings).  There is no advantage mechanically to hit an "nice even number".  However, in some cases, insurance for example, is impacted by engine size.   Your insurance policy may state over a certain size is more expensive...so designers build the maximum value just under that line.  Motorcycles are particularly impacted by this.   In motor racing, (e.g. F1 2015 limit is 1.6 l ) classes of cars are often limited to certain engine sizes.  Again, building to a maximum size *just under* a limit keeps you in spec.