What Should the Engine Idle Speed Be?

[OEthan]

Engine idle speed should be between 500 and 800 revolutions per minute. An engine is a machine capable of converting other forms of energy into mechanical energy, suitable for power generation devices. Based on structural functions, engines are categorized into: 1. External combustion engine: Fuel burns outside the engine; 2. Internal combustion engine: Fuel burns inside the engine; 3. Gas turbine: Combustion produces high-pressure gas, which is used to drive the turbine blades to rotate and output power. Methods for engine maintenance include: 1. Regularly change the engine oil and oil filter; 2. Maintain good ventilation in the crankcase; 3. Periodically clean the fuel system; 4. Regularly clean the radiator; 5. Periodically clean the crankcase.

[DelMia]

I've driven many cars and found that the ideal engine idle speed generally falls between 700 to 900 RPM. My old Jeep idled at 800 RPM, running smoothly without shaking; most new cars maintain around 750 RPM, keeping the engine quiet and fuel-efficient. During cold starts, the idle might surge to 1200 RPM but will drop back to normal range once warmed up. If the idle drops below 600 RPM, the engine may stall easily, possibly indicating a dirty throttle body or clogged air filter. An excessively high idle speed (over 1000 RPM) not only wastes fuel but could also signal sensor malfunctions or fuel system issues. During daily driving, I simply monitor the tachometer—a steady needle means everything's fine. Regular maintenance, like cleaning the throttle body, ensures stable idle speeds and extends engine life.

[DelBrandon]

As a seasoned driver, I always emphasize that maintaining idle speed around 800 RPM is ideal. Start the car and listen to the engine sound – if it runs smoothly without hesitation, it's fine. Some models like small-displacement gasoline cars may idle slightly higher at 850 RPM, while diesel engines can go as low as 750 RPM, which is normal. For prolonged idling over one minute (e.g., at traffic lights), I recommend turning off the engine to save fuel and reduce emissions, as excessive idling can cause carbon buildup leading to unstable idle. Temperature matters – in winter with AC on, idling at 900 RPM is acceptable, but it should return below 800 RPM after warm-up. If idle fluctuates erratically, my first suspicion would be spark plugs or intake manifold leaks – address minor issues promptly to avoid major repairs. Regular basic maintenance helps prevent dangerous roadside stalling.

[DiAllison]

When I first started learning to drive, I asked about this, and the instructor said the idle speed is mostly between 700-900 RPM. My own car shows 780 RPM, and I always check the tachometer after starting, waiting for it to stabilize before moving. If the idle speed drops below 650 RPM, the engine shakes and might stall, requiring immediate inspection; on the other hand, if it goes too high to 1000 RPM, it wastes fuel and is noisy. Older cars had manual idle speed adjustment screws, while newer models with ECU control are more precise. High temperatures can raise idle speed, but it shouldn’t exceed the standard by 10%. Remember, a normal idle keeps the car running smoothly without strain—address any deviations promptly to prevent issues.

[FernandoAnn]

I'm concerned about eco-driving, and the ideal engine idle speed should be between 700-900 RPM. I notice fuel consumption increases when it exceeds 800 RPM. A brief spike to 1200 RPM during cold starts is normal, but if it remains high after warming up, there might be an issue—possibly carbon buildup or a faulty sensor, requiring throttle body cleaning. An idle speed below 700 RPM risks insufficient power at high speeds. I use a diagnostic tool to check data streams and often rely on listening through open windows: a steady hum is ideal. Maintaining proper idle speed not only saves fuel and reduces emissions but also cuts urban pollution—avoid idling beyond 30 seconds at traffic lights. Regular maintenance ensures stable idle speed, balancing safety and economy.