There are three engine modes available: fast (red), neutral (yellow), and power-save mode (light blue). You can switch between the engine modes by tapping them on the left side of the screen for your first driver and on the right side of the screen for your second driver.

Fast mode is the fastest speed mode in the game. When racing in this mode, your Driver will go faster and gain a boost to your Overtaking, Defending, Grip, and Power stats, resulting in faster lap times and more successful overtaking and defending opportunities. However, this mode will also decrease your Fuel, Car Condition, and Tyre wear bars at a faster rate.

Neutral mode is the middle-speed mode in the game. When racing in this mode, your Fuel, Car Condition and Tyre wear bars decrease at a normal rate. 

Power save mode is the slowest speed mode in the game. When racing in this mode, your Driver will go slower and lose some of his Overtaking, Defending, Grip, and Power stats, resulting in slower lap times and less successful overtaking and defending opportunities. However, this mode will also decrease the decline of your Fuel, Car Condition and Tyre wear bars.