Ecodriving is the modern and smart way to save fuel and reach your destination swiftly and – most important – safely. Consuming energy/fuel costs money and causes CO2 emissions and air pollutants with negative environmental impacts. Especially driving with high engine revolutions (high RPM) raises the fuel consumption significantly. Also avoidable sequences of acceleration and braking will lower fuel efficiency. Following the guideline “Safety First”, Ecodriving enables a highly fuel-efficient, smart and relaxed driving style without any loss of time.
It’s a good start to try to follow the tips listed. However, to achieve best possible effects you should also attend an Ecodriving training given by a qualified driving instructor.
There are five basic rules to follow.
- Anticipate traffic flow
- Maintain a steady speed at low RPM
- Shift up early
- Check tyre pressures frequently at least once a month and before driving at high speed
- Consider any extra energy required costs fuel and money
Anticipate traffic flow
- Read the road as far ahead as possible and anticipate the flow of traffic
- Act instead of react – increase your scope of action with an appropriate distance to use momentum. An increased safety distance equivalent of about 3 seconds to the car in front optimises the options to balance speed fluctuations in traffic flow – enabling steady driving with constant speed (see also additional explanation #1).
- Make maximum use of the vehicle’s momentum. Three different techniques are applicable (within 2 categories: (i) in gear; (ii) in neutral) – consider details of the car’s manual (see also additional explanation #2)
Additional Explanation #1:
Systematically increasing vehicle-to-vehicle distance within traffic flow significantly improves overall road safety. Increased safety distance equivalent of around 3 seconds to a vehicle driving ahead optimises options to act instead of only react and reduces risky situations. Key action: Step off the accelerator if traffic flow is slowing down to keep safety distance. With this simple action speed fluctuations in traffic can often be equalised and gently managed. As a result (strong) braking – while wasting built-up kinetic energy – can be often avoided as well as the need to accelerate after too hard deceleration.
Additional Explanation #2:
Making use of vehicles’ momentum means to use built-up kinetic energy of the car most efficiently. The overall goal is letting the car roll and driving steady speed whenever possible instead of braking and subsequently accelerate. Using vehicles momentum three different techniques are applicable – classified in two categories. It is important to consider specific advices of the individual car’s manual as well as strictly follow national legal requirements.
Using momentum can be realised within two different categories of driving techniques:
(i) in gear, (ii) in neutral – resulting into three specific advices.
(i) “using momentum in gear”
Driving technique #1: Let the car roll in gear. The speed of the vehicle will reduce due to the engine’s braking effect via mechanical friction (as gear engaged). Using the right gear unintended acceleration (e.g. while driving downhill) can be avoided. This technique is beneficial to saving fuel if the respective engine has a fuel cut-off mode and also while driving at higher speeds (consider advice for engine’s fuel cut-off).
(ii) “using momentum in neutral”
Driving technique #2: Let the car roll in neutral (no gear engaged with idling engine). The technique rolling in neutral with no gear engaged (with idling engine) makes better use of a
vehicle’s kinetic energy because there is no engine braking effect. This is beneficial for situations like approaching an obstacle or an identified stop (red traffic lights; Stop-sign). Thus, a relative long distance can be driven at quite constant speed without additional acceleration. While rolling in neutral the fuel consumption is defined by the idling engine alone. Especially for cars without engine fuel cut-off mode this is a good technique to use vehicles’ kinetic energy. But also for cars with fuel cut-off the option to letting the car roll without gear engaged can save fuel at typical low speed driving in cities (esp. when “stop-and-go” or only little faster). Engine’s fuel cut-off does not work at low RPM (check with the car’s manual for details), and is activated beyond a specific engine speed for the individual car. For safety reasons while driving downhill it is important to always stay in the right gear to avoid unintended acceleration.
Driving technique #3: Letting the car roll in gear, but with clutch engaged This technique is advisable in situations when it can be assumed that the ride can be continued soon in the same gear, and the use of the engine’s fuel cut- off and engine braking effect is not useful for good fuel efficiency.
Consider: Make use of the engines fuel cut-off whenever useful
It is important to know that inner mechanical friction (of engine/ transmission) wastes more kinetic energy than letting the car roll without traction (no gear engaged or clutch engaged). Engine fuel cut-off (if available for a specific car) operates only at certain speed range and revs area which differs from car to car. It is useful to know the car’s specifics as from the owner’s manual. At low RPM and low speeds (below 50 kph) – as typical for driving in cities – the use of the engine’s fuel cut-off is not always possible and useful. Especially for city driving it can be extremely difficult and distracting – safety risk! – to identify the right gear for making best use of the engine’s fuel cut-off. Relevant for safe driving is the fact that some modern cars accelerate automatically if the car falls below a specifically defined (engine) speed. This effect – if unintended – should be avoided because it raises fuel consumption and may lead to driver’s irritation (road safety issue). Older cars mostly have no engine fuel cut-off mode.
Note: All three techniques are to be applied strictly following the guideline “Safety First”.
Maintain a steady speed at low RPM
- Drive smoothly at low RPM using the highest possible gear (See also additional explanation #3.1)
- Remember driving at high speeds or with high RPM significantly increases fuel consumption (See also additional explanation #3.2)
Additional Explanation #3:
3.1. Smooth driving with steady speed saves a lot of fuel compared to the same average speed, but with sequences of acceleration and braking. Unnecessary speed peaks and abrupt braking do not only waste fuel, but also raise the stress level while driving and causing additional safety risks. Ecodriving strives for a smooth driving style allowing undisturbed, easy floating within traffic. Using a cruise control can be advisable to support a smooth ride, especially for extraurban driving (rural roads or highways), but also some traffic situations in city driving.
3.2. High speed driving or driving with high RPM leads to a drastically increased fuel consumption Especially for city driving there is nearly no chance to increase average speed or gaining time advantage with strong acceleration and speed peaks. The time you need for a ride is dominated by external factors (like traffic density, traffic lights, etc.). Even
on highways the time saving potential is quite low and has to be (over-)paid with drastically increased fuel consumption. Even getting a little bit faster means higher RPM plus aerodynamic drag, even within speed limits (e.g. 110 to 120 kph), and more fuel has to be burned and money wasted (see on-board vehicle computer).
Shift up early
- Shift to higher gear at approximately 2.000 RPM
- Consider the traffic situation, safety needs and vehicle specifics (See also additional explanation #4)
Additional Explanations #4:
Driving with high or even medium engine RPM always consumes more fuel then driving at low RPM at whatever speed. Therefore, early shifting is highly recommended. However, vehicle specifics and also given traffic situation has to be taken in account.
Rough guidance for shifting and steady speed driving (on the flat, not uphill):
1st Gear: Driving-off only (one vehicle length)
2nd Gear: 20 kph
3rd Gear: 30 kph
4th Gear: 40 kph
5th Gear: 50 kph
6th Gear: 60+ kph
Based on the rough guidance for steady speed driving (on the flat, not uphill) the optimum gear shifting for each car has to be identified individually. Full throttle acceleration should be avoided if the acceleration can be chosen individually. When driving uphill choose a gear which does not require fully pushing down the accelerator to keep an acceleration reserve (safety issue). As appropriate accelerator pedal position 2/3 or 3/4 should be chosen.
Note: “Safety First” guideline also applies for acceleration! For strong acceleration required (e.g. overtaking, lane changing, driving onto a highway) use intentionally full throttle acceleration “pedal to the metal” to quickly achieve the speed envisaged and safely manage the specific situation.
When accelerating stronger skipping gears can help to save fuel. Skipping gears is meaningful and fuel-efficient to reach faster a targeted final (steady) speed and keeping it for a longer time.
Engine torque curves of diesel and petrol cars differ strongly, also when comparing older and advanced engines in general (irrespective of fuel sort). Cars with diesel powered engines or advanced direct injection gasoline engines can be shifted up at even lower RPM than (older) petrol powered cars.
Specific advises for automatic transmission:
To drive fuel-efficient avoid kick-down to accelerate excepted when it is required for safety reasons (see above).
To intentionally shift up and ride with lower RPM with automatic transmission simply step-off the accelerator shortly.
Shifting and driving at low RPM is harmless to any engine or car! Overloaded/blocked particulate filter of diesel cars do not result from driving with low RPM, but relate to low engine temperature at too many short trips (also to be avoided due to high fuel consumption). If necessary a 10 minute lasting highway ride can prevent blocking the particulate filter. Please also see details and practical instructions in the car’s manual or from car manufacturer directly. In general it is advised to select and buy a car that fits to the use pattern and trip structure.
Check tyre pressures frequently at least once a month and before driving at high speed
- Keep tyres properly inflated as low tyre pressure is a safety risk and wastes fuel
For correct tyre pressure (acc. to loading, highest pressure and speed driven), check with car’s manual.
Consider any extra energy required costs fuel and money
- Use air conditioning and electrical equipment wisely and switch it off if not needed
Electrical energy is converted from extra fuel burned in a combustion engine, so electrical equipment doesn’t work “for free” – it always costs extra energy and money.
- Avoid dead weight and aerodynamic drag