20 Driving Habits Many People Get Wrong

The idea sounds logical enough: if the transmission is in neutral while the car rolls downhill, surely the engine must be using less fuel. Modern fuel-injected vehicles make that assumption unreliable. During deceleration while the car remains in gear, the engine-management system can reduce fuel delivery dramatically and, in many conditions, cut it off temporarily. In neutral, the engine still has to receive enough fuel to keep idling. There is also a driving reason to leave the transmission engaged.