What is the gauge on the left side of the dashboard?

[OSophia]

Due to different vehicle models, the design of the car dashboard may vary. In most conventional cars, the leftmost gauge on the dashboard is the water temperature gauge. However, in some cars, the left gauge is not the water temperature gauge but a tachometer with numbers ranging from 0 to 8. The dial of the tachometer is larger than that of the water temperature gauge and is used to measure the engine's RPM. Generally, when the tachometer needle is in the white scale area, it indicates a safe RPM range, while the red scale area represents a dangerous RPM range. When driving, the water temperature gauge should normally indicate the middle line or slightly higher. If the water temperature is found to be too high or too low, immediate maintenance is required. If the water temperature is too high, the car must be stopped immediately and not driven further. If the water temperature is low, you can drive to a repair shop for inspection. The water temperature gauge is marked with the letters "C" and "H" or uses white and red areas to distinguish. "C" is the first letter of the English word "cool," meaning cold, while "H" is the first letter of the English word "hot," meaning hot. The sensor of the water temperature gauge is a thermistor-type sensor, fixed with threads on the engine's cooling water passage. The thermistor determines the current flowing through the coil winding of the water temperature gauge, thereby driving the pointer to swing. In the past, tap water was used as the cooling water for car engines, but now many car engine cooling systems use specialized coolant, hence it is also called the coolant temperature gauge.

[LeXavier]

After driving for so many years, the gauge on the left side of the dashboard is the tachometer. Every time I start and shift gears, I have to glance at it. The needle feels most comfortable between 1500 and 2500 RPM—too high and the engine roars, too low and it might stall. If it hits the red zone on the highway, I need to ease off the throttle immediately to avoid engine damage. New drivers often focus on the speedometer, but the tachometer is what really matters, especially in manual transmission cars—it tells you when to shift. If the needle jumps around while idling at a red light, it’s likely a sign that the throttle body is dirty and needs cleaning. Making a habit of watching the tachometer helps drive more fuel-efficiently and safely.

[LeZoey]

During driving lessons, the instructor always emphasizes checking the tachometer—that small round dial with numbers in front of the steering wheel. The needle ranges from 0 to 8, representing thousands of engine revolutions per minute. Automatic transmission cars shift gears on their own, but manual transmissions rely on it to determine the right shifting moment. Shifting around 2000 RPM ensures the smoothest ride, below 1500 RPM the car may shake, and above 3000 RPM consumes too much fuel. Especially when climbing hills, if the needle starts dropping, you need to downshift and give it more gas, or the car will struggle. I remember stalling a lot when I first started driving—just didn’t understand this gauge. Now, it’s the first thing I instinctively check every time I get in the car.

[LeEzra]

The one on the left is the tachometer, showing how fast the engine is running. The numbers marked ×1000 indicate the RPM, for example, 2 means 2000 revolutions per minute. In an automatic transmission car, it shifts gears automatically, while in a manual transmission, you need to change gears based on the RPM. For manual cars, maintaining around 2000 RPM is the most fuel-efficient. During rapid acceleration, the RPM will spike, and when climbing steep hills, you should downshift if the RPM is too low. Keeping the RPM above 3000 for extended periods wastes fuel and harms the engine. At idle, the needle should stay around 800 RPM when at a red light. If the needle jumps erratically at idle, it's best to get it checked at a repair shop immediately.