What is the appropriate idle speed for a car?

[Samuel]

Engine idle speed should be around 850 RPM. For cold engine idle, the range should not exceed 1200 RPM. Small-displacement vehicles typically have an idle speed close to 700 RPM, while large-displacement vehicles may approach 1000 RPM. Car idle refers to an operational state where the engine runs without load, meaning the vehicle is in neutral gear. The engine speed during this state is called idle speed, which can be adjusted by regulating the throttle opening. Idle operation means the engine is "working without output." When the accelerator pedal is fully released while the engine is running, it enters idle operation. During idle speed adjustment, sudden increases or decreases in RPM should be avoided as they may cause premature engine wear. It's recommended to have this adjustment performed at automotive service centers. The minimum stable engine speed when starting a stationary vehicle is called parking idle (the process where a cold engine transitions from cold idle to normal operating temperature idle is called warm-up or hot-running).