A low consumption doesn't always mean lower costs in general. To keep the expenses down, one must also consider the expected cost of repairing the vehicle and it's lifespan. Unfortunately, far too few buyers of new cars take the trouble of finding out what a standard repair, e.g., brake-pads and discs on the front wheels, will cost. One can also scan the internet to see what the trade-in prices of a particular model are. Another important point is, too many people go out and buy a Diesel powered car and don't drive the kilometers necessary for the calculation to function. Have a look at the kilometers on the clock of a used Diesel, divide the amount by the age of the car, then one can see what kind of service the car has given.

Of course, the Diesel is a fuel saving champion. Indeed, in the manufacturing it is often much more expensive. For this reason, it generally makes sense in the case of large, all-wheel drive cars or if the vehicle does a lot of towing. More compact cars must be driven 20.000 kms per year and more, to make the Diesel worth while. In addition of course, the more Diesel that is used, the more expensive it gets, compared with petrol. One can not produce as much Diesel from crude oil as one likes. Apart from that, the petrol engines are also becomming more and more economical. One can of course, ignore the economic aspect and consciously buy the more expensive Diesel, using fuel- and CO₂ saving as an argument. However, think about this: at the same consumption level, the Diesel expels 13% more CO₂ than the petrol engine does.

There are still other reasons for a low fuel consumption. Among the most important are,
- the weight,
- the size of the vehicle,
- the frontal cross sectional area.
Everybody knows that more weight makes acceleration more difficult and increases the consumption. The height and width of the vehicle are nowadays, not generally taken into consideration. It is not really necessary, to have almost a half a meter of space over ones head. Hopefully, the driver travels slowly, because the front surface area must push the air, because of the unnecessary interior space, out of the way, which means, more fuel must be used. The fitting of a tow-bar is - despite the increased weight - more economical. A trailer, borrowed when necessary, will solve any transporting problems and one does not have to always lug the empty space around.

The styling and shape are often even less considered. There are a number of mid-size and luxury class vehicles which could serve here as an example, despite their large cross-section surface they have an astonishingly low wind resistance. This is obvious if you compare the engine performance with the available top speed.
What else pushes the consumption up? For example, a gearbox layout, which brings the rev-counter over the red line when the top speed is reached. The lower the RPM at the same speed, the better it is for the consumption. As far as spoilers are concerned, it becomes tricky, because there are air- resisting and lift-reducing examples, the latter are probably not suited for the saving of fuel.

Actually, the consumption advertised by the manufacturer is subject to standardisation. Thereby, the rolling friction and the air-resistance are determined by coasting tests then, with these stress values, the cars are driven on the test bench at pre-determined cycles. However, when one compares the advertised consumption with the values attained in real life, one feels one should question the honesty of the manufacturers. It may help to ask around in ones circle of friends or to check out a few suitable Internet forums. Those who are really cautious, may rent the model for a while to come to their own conclusions, indeed, patience is necessary, it may take some time before one can obtain the desired model, with the respective specifications, from the rental agency. 02/08