When the clutch is engaged, the engine is directly connected to the transmission and wheels. This allows the engine to power the vehicle and move it forward. When the clutch is disengaged, the engine is disconnected from the transmission and wheels. This means that the engine is still running but is not powering the vehicle.
In fifth gear, the engine is turning at a relatively high RPM. When the clutch is disengaged, the engine continues to run at this high RPM, but it is not doing any work. This can cause the engine to overheat and waste fuel.
Additionally, disengaging the clutch can cause the vehicle to lose momentum. This can make it more difficult to accelerate and maintain a steady speed. As a result, you may end up using more fuel than you would if the clutch were engaged.
For all of these reasons, it is not recommended to press the clutch while running in fifth gear of a four-wheeler.