What is the optimal idle speed for a car?
2 Answers
The optimal idle speed for a car is between 800-900 RPM. Below is relevant information about car idle speed: 1. Situations where idle speed automatically increases by 50-150 RPM: (1) Cold start with low coolant temperature. (2) Battery power deficiency. (3) Air conditioning cooling operation. 2. Hazards of unstable car idle speed: (1) If car idle speed is too high, check for loose or leaking intake manifold, which will significantly increase fuel costs and accelerate engine carbon buildup. (2) If car idle speed is too low, there's a safety risk of sudden stalling while driving. (3) Fluctuating idle speed may indicate non-functioning spark plugs or ignition coils, causing engine piston malfunction and severe vibration.
I've always driven regular family cars, and there's no fixed standard for idle speed—it mainly depends on the vehicle's condition. For ordinary sedans, an idle speed between 600 and 800 RPM is ideal. For example, my car usually idles at around 650 RPM in neutral, running smoothly without shaking. If the idle speed is too low, say below 600 RPM, the car may stall easily and lack power when starting. On the other hand, if it exceeds 1000 RPM, it wastes fuel and creates more noise. It's normal for the idle speed to be slightly higher in cold weather, like 750 RPM during warm-up, or around 850 RPM when the AC is on to ensure compressor operation. I recommend glancing at the dashboard after starting the car—the green zone indicates normal operation. If the idle speed is unstable, check the air filter or spark plugs immediately, and avoid adjusting it yourself. Regular maintenance can prevent carbon buildup and keep the idle speed in optimal condition, as safety and comfort are what matter most.
