A driver wants to minimize fuel consumption while descending a long, steep mountain pass. Which of the following driving practices is correct according to the DGT?

A)Shift the gear lever into neutral (punto muerto) to allow gravity to coast the vehicle downward without using fuel.
B)Keep the vehicle in a suitable gear without pressing the accelerator pedal, utilizing the engine brake to control speed safely.Correct
C)Turn off the engine and vehicle headlights entirely if visibility is clear, as this eliminates engine consumption and saves an additional 2% of electrical fuel load.

  • The Danger of Neutral: When you put a car in neutral on a descent, you completely disconnect the engine from the wheels. This eliminates the engine brake (freno motor). The vehicle will continuously gain momentum due to gravity, forcing you to ride the brake pedal. This excessive friction causes the brakes to overheat, which can boil the brake fluid and lead to a sudden, catastrophic loss of braking efficiency (known as brake fading).

  • The Danger of Turning off the Engine/Lights: Turning off the engine while moving is incredibly dangerous. It immediately deactivates power steering and the brake servo, making the car nearly impossible to steer or stop. Furthermore, turning off headlights to save a minor 2% of fuel reduces your visibility to other drivers, creating a severe accident hazard.

  • Why Gear Engagement Wins: Modern fuel-injection electronic systems are highly advanced. When you lift your foot completely off the accelerator while a gear is engaged on a descent, the vehicle's computer cuts fuel injection to the engine entirely (0.0 L/100km consumption). The wheels keep the engine turning mechanically, which provides natural braking resistance (engine brake) to control your descent safely while costing absolutely nothing in fuel.

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