What is the engine speed when the car is at 120 km/h?

[ElleFitz]

When the car is at 120 km/h, the engine speed is around 3500 RPM. Under normal driving conditions, the engine speeds at the highest gear are as follows: when the speed reaches 100 km/h, the engine speed is generally around 2800 RPM; when the speed reaches 110 km/h, the engine speed is generally around 3200 RPM. The reasons for high engine speed include: 1. Sudden increase in throttle opening; 2. Fuel injector leakage or blockage; 3. Slippage or damage to the air conditioning clutch; 4. Air intake system leakage; 5. Insufficient engine power output. Solutions for high engine speed include: 1. Adjusting the throttle opening; 2. Replacing the fuel injector, air conditioning clutch, air intake system, or engine. Driving precautions include: 1. Avoid emergency braking and rapid acceleration during the break-in period; 2. Do not overload the car within the first 1000 kilometers of driving; 3. Observe speed limits during the break-in period and ensure moderate speed driving; 4. Avoid driving for excessively long periods, allowing the car time to adjust; 5. Change the engine oil as specified by the manufacturer during the break-in period; 6. Avoid driving at a constant speed for prolonged periods.

[StJackson]

At a car speed of 120 km/h, the RPM is not a fixed value. It depends on your car type and driving habits. Having driven for nearly twenty years, my experience tells me that there are significant differences between cars. For automatic transmission cars, like the sedan I drive, the RPM is around 2500 to 3000 when cruising at 120 km/h on the highway, which is smooth and fuel-efficient. For manual transmission cars, if the right gear is selected, such as a five-speed car, it might be around 3000 RPM, but it could be higher if you're in a higher gear. Sporty cars like some SUVs might approach 3500 RPM because their engines are more powerful and run at higher RPMs. Additionally, the gear ratio of the transmission is crucial. For example, long-wheelbase cars are designed for efficiency and can run at lower RPMs. Road conditions also play a role—going uphill might increase the RPM, while downhill could decrease it. In short, as long as the RPM is within the normal range and there are no unusual noises during daily driving, there's no need to worry. However, if it's too high, like exceeding 4000 RPM, it might be consuming more fuel, and you should check it out.

[AnaMarie]

From a technical perspective, the RPM at 120 km/h is the result of a combination of engine output and gear ratio. I often study these factors, and there are quite a few influencing elements. Automatic transmission systems adjust gears in real-time to match the load, typically fluctuating between 2000 to 3500 RPM during steady highway driving. For manual transmissions, it depends on the gear selected—choosing the highest gear usually results in around 2500 to 3000 RPM. However, the actual value is affected by vehicle weight and air resistance. Engine type is crucial: smaller-displacement turbocharged engines may run at slightly higher RPMs to compensate for torque, while larger-displacement V6 or V8 engines can easily maintain a lower RPM of around 2400 at 120 km/h. Economy cars, such as hybrids, are designed to prioritize low RPMs, potentially as low as 2000 for fuel efficiency. However, an OBD scan is needed for precise readings. It's advisable to monitor the dashboard while driving and maintain a steady state for better efficiency. Don’t overlook the risk of overheating caused by prolonged high RPMs.

[FaithDella]

My car is a family automatic transmission model, and the RPM is around 2700 at 120 km/h. After driving for a long time, I've learned some basics. RPM varies by car and brand—Japanese cars might be lower, while European cars could be higher. With manual transmissions, choosing the wrong gear can push RPM up to 4000, which consumes more fuel. Low RPM, like below 2500, might cause lugging and affect power. For daily driving, as long as the RPM is appropriate, it's fine. Abnormally high RPM indicates a problem that needs repair.