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Eco Driving
Eco driving is a popular initiative (typically promoted
by European governments) that aims at popularizing the concept of energy
efficient driving attitudes among the professional and general driving public.
There are five basic rules to follow.
Shift to a higher gear
Shift up between 2000 and 2500 RPM. This
applies to both gas and diesel powered cars.
Part of the power of a passenger car's engine is
lost by mechanical friction. These losses increase with engine speed. By
driving at low engine speeds these losses remain limited, which reduces fuel
consumption. The efficiency of a car's engine also increases when a high
engine load is used (giving more gas at low engine RPM [Revolutions
Per Minute]). Under these conditions the engine power is
generated more efficiently. During acceleration the most efficient way of
driving is therefore to shift up as soon as possible (at low engine speed)
and to apply a relatively high load on the engine. Driving in a high gear
automatically requires a high engine load to keep up with traffic.
In order to use the efficiency of a car engine in an
optimal way, a maximum engine speed of 2500 RPM for shifting is recommended
for gas engines. Because diesel engines generally reach their optimal
efficiency at lower engine speeds, a maximum engine speed of 2000 RPM for
shifting is recommended. An RPM gauge (tachometer) is a useful tool in
determining the right shifting moment. This shifting recommendation is most
often applicable to cars with a manual gearbox, but it can also partly be
applied by cars with an automatic transmission. To cause an early
shifting on an automatic transmission briefly release the gas a little to
prompt to software to shift the the transmission to a higher gear.
This will only work in this way if the transmission is set to "D".
Early shifting as recommended above is in no way
harmful to a properly maintained engine.
Maintain a steady speed
Maintain a steady speed, using the highest gear
possible!
When accelerating, energy in the fuel is used to
propel the car. Part of this energy is wasted when you brake. You may
experience this phenomenon after hard braking; the brakes have become very
hot because of the transformation of propulsion energy into heat. Therefore,
repeated acceleration and braking requires a lot of energy (fuel).
This can also be explained by the fact that the
average car only needs 5 kW of power to drive at a steady speed of 50 km/h.
Conversely a car traveling at 120 km/h, the amount of power needed increases
to approximately 25 kW. The remaining 90% (or more) of the engine's power is
only needed for acceleration or for driving at very high speeds. By driving
steadily as much as possible, the loss of energy and fuel remains the
lowest possible. Always try avoiding unnecessary accelerations and braking.
Cruise control is a useful aid for smooth and steady driving particularly on
leveled highways. If traveling at highway speeds and beginning a hill
climb, exit the cruise control mode and instead control the gas pedal gently
allowing for some of the speed to bleed of. This will keep the engine
RPM at lowest level possible thus improving your Fuel economy.
Driving at steady speed on leveled roads not only
increases fuel-economy, but it also has a positive effect on exhaust
emissions, traffic safety, traffic flow and passenger comfort.
High gear and low engine RPM
As already mentioned, the power needed to drive at a
steady speed is rather low. Therefore, a high gear can be engaged without
any problem at low engine speeds. This saves fuel and is in no way harmful
to the engine, especially when it is properly maintained
The opinion that the accelerator pedal is directly
fixed to the fuel consumption is often incorrect for a typical gas engine. The
accelerator pedal operates only the throttle valve which is responsible for
controlling the amount of air entering the engine. On the basis of this
throttle control and also other factors such as the engine RPM, the fuel
quantity used is calculated by the engine control unit. Each small reduction
in the level of revolutions means that less fuel is needed.
Look ahead as far as possible and anticipate to surrounding traffic!
In order to drive at a steady speed (as discussed
above), it is important to anticipate to surrounding traffic to avoid
unnecessary braking and accelerating. For example, when:
- Approaching traffic lights...
- Overtaking traffic like cyclists or
agricultural vehicles...
- Driving on a busy highway...
... and also anticipating a variety of other traffic can have a big
influence on how steadily you drive.
Many situations can already be noticed far ahead,
long before approaching the situation itself. In case you use cruise control
(see recommendation 2) you will have to anticipate even more to be able to
make full use of its benefits.
Decelerate smoothly
When you have to slow down or to stop, decelerate
smoothly by releasing the accelerator in time, leaving the car in gear!
Gas and diesel cars manufactured from 1990 onwards,
are generally equipped with fuel injection combined with an electronic
function that cuts off the engine's fuel supply under engine braking
(accelerator released and a gear engaged). The advantages of this fuel cut
off function can be used by releasing the accelerator in time, for example
when approaching traffic lights. This also reduces wear and tear on the
brakes, reducing maintenance costs. Engine braking, not only has a positive
effect on fuel consumption, but also on exhaust emissions, traffic safety,
traffic flow and passenger comfort.
In case of less modern cars with a carburetor and
older diesel cars (generally manufactured before 1990), it makes no
difference whether you decelerate with gears engaged or disengaged, for the
carburetor is a mechanical device that is not equipped with electronics to
cut off fuel supply. These cars consume an equal amount of fuel under engine
braking and when idling. However, releasing the accelerator in time still
avoids hard braking and improves the durability of the brakes.
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