Texas CDL General Knowledge Practice Exam

When driving a manual transmission vehicle, the tachometer can help you determine the optimal time to shift gears. This is because the tachometer measures the engine's revolutions per minute (RPM), which can indicate when the engine is working too hard or idling too slowly. Option B is incorrect because double clutching can be helpful in some situations, such as when driving on a steep incline or when downshifting. Option C is incorrect because shifting gears too quickly can cause the vehicle to jerk and potentially lose control. And option D is incorrect because shifting gears abruptly can actually cause more fuel consumption and put unnecessary strain on the engine.