Ecodriving Techniques
Shift to a higher gear as soon as possible
As a rule for efficient acceleration, change up to a higher gear at no more than 2500rpm in a petrol car 2000rpm in a diesel. (diesel engines reach thier optimal efficiency at lower engine speeds)
The reason for keeping an engine's speed down is that some of an engine's power is lost to internal friction, which increases with engine speed. Driving at low engine speeds therefore limits the losses and reduces fuel consumption.
The efficiency of a car also increases when a high engine load is used. When accelerating, the most efficient way of driving is to shift up early whilst putting your foot down relatively hard (deep accelerator position).
This is becuse the accelerator works the throttle/butterfly valve and consequently affects the flow of air to the engine. The quantity of fuel to be injected into the engine is then calculated by the engine management system using parameters including the position of the accelerator pedal, engine speed and air temperature.
Automatics
The advice to shift up early but apply a high load to the accelerator does not work with cars with automatic transmission. This is because an auto box interprets heavy acceleration as meaning that the driver wants to accelerate quickly. Therefore, drivers of automatic cars should accelerate gently as this encourages the auto box to shift up at lower speeds. The "sports" mode should also be avoided.
Maintain a steady speed using the highest gear possible
Driving at a moderate, steady speed requires relatively little energy. An engine's full power is only used during hard acceleration or at very high speeds. When a car brakes, energy is lost, ending up as heat in the brakes. Therefore, driving steadily and avoiding unnecesary acceleration and braking therefore reduces fuel consumption. It also has a positive effect on exhaust emissions, traffic safety, traffic flow and passenger comfort.
Slow down
The most efficient speed is dependent on the car in question but is typically around 45-50mph. Above 65 or 70mph fuel consumption increases significantly with speed. For example, driving at 80mph instead of 70mph will add around 10-15% to fuel consumption.
Anticipate traffic flow
Read the road as far ahead as possible to anticipate situations before they arise. This is essential in order to be able to drive at a steady pace and avoid unnecessary braking and acceleration.
Decelerate smoothly
When slowing or stopping, decelerate smoothly by releasing the accelerator as soon as possible, leaving the car in gear. Petrol and diesel cars made from 1990 onwards are generally fitted with fuel injection systems that include a function that cuts off engine fuel supply under engine braking conditions (accelerator released and a gear engaged). Under such conditions a car uses lessfuel than it would if it were coasting in neutral. Driving to maximise the use of engine braking not only has a positive effect on fuel consumption and emissions, but also on traffic flow, traffic safety and passenger comfort.
