The weight of the automobile is of great importance for the fuel consumption. Indeed, the old rule of thump that 100 kg increase in weight cause an additional fuel consumption of 1 l/100 km does
not hold any longer, but, nevertheless, the weight does impose its effect on every acceleration process. Although light metals and plastics are used in the design, improvements for the passenger's
protection and comfort accessories more than compensate the achieved results. The vehicles become ever heavier. In addition, accessories (like air-conditioning, or four-wheel drive) force up the
fuel consumption directly or indirectly through the generator.
|Technically much has been achieved,|
but not enough for a long time
Successful savings are achieved rather due to lower air resistances of the car bodies. However, also they are more than made up for by the higher and broader designs and the increased safety
Higher savings rates seem possible by developing new engines. The diesel engine with direct injection seems most promising, as the engine also allows an economical driving manner at low revs.
Unfortunately, the diesel oil consists of approx. 13% more carbon portions as compared to petrol fuel. Thus, it
must be at least this much more economical than the petrol engine to achieve an ecological savings effect, too.
The petrol engine still has potentials for lower fuel consumption featuring the direct injection and the fully variable compression and/or valve control without throttle valve.
Also the transmission technology has progressed. While the customary fully automatic
transmission system rather increases the fuel consumption, the new sequential gearboxes have a positive effect on the fuel consumption due to suitable gear switch programs without decreasing
the efficiency in the drive train.
|Economical driving above the idling speed|
The diagram (on top) clearly shows the influence of the number of revs on the mileage in part load. Having the same power output of only 20 kW the engine can use with 5500 1/min more than
330 g/kWh or with approx. 2000 1/min less than 270 g/kWh. Because the achievement is the same in both cases, the additional fuel consumption for a certain distance amounts to approx. 25%.
There is more. At 17.5 kW and about 2000 1/min a consumption of 240 g/kWh can be reached. It rises to 270 g/kWh at 10 kW and approx. 1200 1/min. If the specific fuel consumption (in
g/kW) increases by approx. 11% and at the same time the effective output declines by approx. 40%, the distance mileage has presumably been decreased once again. The fuel consumption is
fewest just above idling speed in the highest gear. The world record with more than 3000 km/liter (converted) on special vehicles shows the potential of the fuel. Slightly prepared normal petrol
engine vehicles with (however, dangerous) long-term journeys on the highway at 60 km/h in the highest gear also manage a fuel consumption of approx. 3L /100 km. Basically, shifting gears
upwards affects the fuel consumption positively - at the same speed. With this method you can achieve without any further limits in the driving speed up to 1 liter of savings on 100 km.
|Number of accelerations and speed -> consumption|
You can recognize a driving manner that saves fuel also by analyzing the braking wear. The higher the break wear, the more fuel was used. A farsighted driving manner, timely easing of the
accelerator pedal, or (better!) idle running and engine off in front of the red traffic lights clearly lower the fuel consumption in the city. This should be worthwhile, assuming an operation-warm
engine, already after approx. 20 seconds, for the petrol-driven car even a little shorter, for the diesel a little longer. In the city and on the country roads you have the highest savings potential. It
pays off to drive far-sighted and adapted to your surrounding. On the highway there is a clear dependence between fuel consumption and driving speed or acceleration processes.
Some drivers apply classical offences against the savings strategy and the environment. There is the warming up of the car engine in the winter while defrosting the windows. This produces
unnecessary pollutants and is also extremely unhealthy for the engine. Tests show that an engine needs approx. 20 minutes to reach its operating temperature when standing still, while it is 5 minutes
when driving. Generally, the wear is high due to cold starts especially for petrol engines. Therefore, it is advisable to combine several trips, especially during the winter.
The fact that pointless roof racks and heavy parts should not be left behind in the boot and the correct or slightly raised tire pressure is quite natural. Small savings effects are also caused by light
wheel bearings and tires, and (fully) synthetic oils.