Is RPM per second or per minute?

[VonHazel]

Generally, it is per minute. The normal range for a car's tachometer is 2200-2500 RPM. Cars have a tachometer needle, so drivers can roughly control the engine speed. While driving, the optimal engine speed is around 2200-2500 RPM. Regardless of the gear, it's best to maintain the engine speed within this range. Too low RPM will make the car sluggish, waste fuel, and damage the engine; too high RPM increases unnecessary fuel consumption and also harms the engine. Below is an introduction to automatic transmission gears: 1. L Gear: Low gear, which limits speed. When climbing a hill, using this gear maintains high RPM at a low gear. 2. S Gear: Sport mode, where the transmission can shift freely but delays shifting to keep the engine at high RPM for a longer time, allowing the car to move at low gear and high RPM. 3. D Gear: Drive gear, used for forward movement. 4. N Gear: Neutral gear, used for brief stops. 5. P Gear: Park gear, used when parking to engage the parking brake and prevent the car from rolling. 6. R Gear: Reverse gear, used for backing up. However, R gear should only be engaged when the vehicle is completely stopped; shifting into R while the car is still moving slowly can cause severe damage to the transmission.