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Question

Difficulty: MediumEnvironmental Impact and Fuel Efficiency

You are driving away from a junction and accelerating onto an open road. How should you manage gear changes to maximise fuel efficiency and minimise environmental impact?

  1. A
    Shift into neutral and coast between gear changes to maintain momentum
  2. Change up into a higher gear as soon as possible without labouring the engineAnswer
  3. C
    Hold low gears at high engine revolutions to clear dashboard emissions warning lights
  4. D
    Accelerate hard in first gear until reaching the speed limit before selecting top gear

Answer

Change up into a higher gear as soon as possible without labouring the engine
Changing up smoothly into higher gears as early as possible—without causing the engine to struggle or labour—keeps engine speeds low. Operating at lower RPM uses less fuel, reduces mechanical wear, and decreases harmful exhaust emissions.

Step-by-Step Solution

1
Identify the primary mechanical factor governing engine fuel consumption during acceleration
Engine speed (measured in revolutions per minute or RPM) directly affects fuel injection rates and mechanical friction.
Higher engine revolutions burn significantly more fuel and produce greater exhaust emissions for each mile travelled.
2
Apply eco-safe driving techniques for manual and automatic transmissions
Shifting smoothly into higher gears early (typically around 2,000 RPM in diesel vehicles and 2,500 RPM in petrol vehicles) maintains moderate engine speeds without causing the engine to labour.
Keeping engine revolutions within an optimal, lower rev range delivers required road speed with the least amount of fuel.

Key Concept

Eco-safe gear shifting technique and engine efficiency
Estimated Time:45s
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Topics

Environmental Impact and Fuel Efficiency

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