What is the normal engine speed?

[VanRobert]

The normal engine speed is generally between 700-800 RPM. If the speed is too low, the engine is prone to shaking; if it's too high, it will increase fuel consumption. As long as there is no shaking, design engineers prefer to keep the speed as low as possible to save fuel. Under the following conditions, the idle speed will automatically increase by 50-150 RPM: 1. Cold start, when the water temperature is low; 2. When the battery is low on power; 3. When the air conditioning is turned on for cooling. Unstable engine idle speed can lead to the following hazards: 1. If the car's idle speed is too high, check whether the intake manifold is loose or leaking. This will significantly increase fuel costs and also lead to more engine carbon deposits. 2. If the car's idle speed is too low, there is a safety risk of stalling while driving. 3. If the car's idle speed fluctuates, it might be due to spark plugs or ignition coils not working properly, causing the engine to misfire and shake severely.

[OKing]

Last time my friend was driving a manual and asked how to read the tachometer, I just told him to look at the steering wheel: in normal city driving, it's around 1500 to 2000 RPM, and cruising on the highway at just over 2000 RPM is the quietest. If you floor it to overtake, 4000 to 5000 RPM is perfectly normal. When starting a cold engine, it might jump to 1200 RPM, but after waiting about ten seconds for the coolant temperature to rise, it'll drop to around 700 RPM on its own. Remember, as long as it's not making weird noises like a power drill buzzing wildly, higher RPMs are fine. However, experienced drivers often watch the tachometer to shift gears, while automatic transmission cars are more worry-free since the computer finds the most comfortable range on its own.

[Genesis]

After driving a taxi for twenty years, I've touched more engines than passengers I've seen. Don't panic when a new car's RPM jumps to 1200 right after starting—just wait half a minute and it'll surely drop below 800. On the highway, keeping it just over 2000 RPM is the most economical, usually marked in green on the dashboard. When climbing hills or hauling heavy loads, revving up to 3000 RPM is normal. My old Jetta, with 800,000 kilometers on it, still idles steadily at 600 RPM. If you notice the needle shaking for no reason or the tachometer dancing when you press the gas, get it checked immediately—it's likely the spark plugs or throttle need cleaning.

[VonJordan]

Back when I was getting my driver's license, the instructor taught me a rhyme: idle at 680 rpm, accelerate around 2000 rpm, and go all out at 4000 rpm for overtaking. Nowadays, automatic transmission cars find the optimal rpm on their own, so there's no need to worry about it. However, there are a few special situations to watch out for—when idling at a red light with the AC on, the rpm may increase by 200-300; when braking hard, the auto start-stop system will bring the rpm to zero; and when descending a long slope in a lower gear, the rpm might shoot up to 3000 while the speed remains low. For the first two years, a new car's rpm is particularly stable. If the idle rpm fluctuates by more than 50 rpm after 50,000 kilometers, it's time for maintenance!