Experts agree that for decades to come, the diesel engine will continue to be the backbone of the drive system for heavy commercial vehicles. This is supported by a dense, well-established worldwide infrastructure ranging from fuel supplies to ser­vices, as well as the diesel’s reliability and unrivalled cost-effectiveness. One major aspect of this cost-effectiveness is a low fuel consumption, which also repre­sents a contribution to the conservation of resources.

At the same time the diesel engine demonstrates its great potential by a continuous reduction in emission levels. Compared to 1990 (Euro 0), modern diesel engines in trucks and buses certificated to Euro 5 emit around 90% fewer particulates and nitrogen oxides (- 86% particulates, - 98% nitrogen oxides).

Diesel engines are often referred to as a conventional drive system, however owing to continuous improvement, these units have long been high-tech developments with highly sophisticated control of an efficient powertrain.

In Europe the name of this fuel-saving formula is BlueTec: at the end of 2004/be­ginning of 2005 Mercedes-Benz was the first brand to introduce econo­mical and environmentally friendly BlueTec technology in its heavy trucks. With its optimised combustion and exhaust gas aftertreatment using the additive AdBlue, BlueTec technology is perfectly suited to European emissions legislation and operating parameters.

Starting with vehicles for heavy long-distance haulage, the range of BlueTec 5 vehicles has meanwhile been extended to include light trucks for distribution operations. Well before the European emission standards Euro 4 and Euro 5 come into force, the company is therefore able to field extremely economical and environmentally compatible vehicles.

Compared to other exhaust gas aftertreatment systems, pioneering BlueTec tech­nology saves around 1500 to 2000 litres of fuel over the usual annual mileage of a long-distance truck. Extrapolated to a population of around 100,000 trucks with BlueTec technology, this represents a total saving of around 150 million litres of fuel per year, or the payload of around 5000 fuel tankers. Thanks to optimised com­bustion, there is also a significant reduction in emissions of particulates, including fine particulate matter.

The considerable reduction in fuel consumption is based on highly developed engine technology. This includes optimally shaped combustion chambers, fuel injection technology with enormous injection pressures for ultra-fine fuel atomi­sation to ensure optimal combustion, individual control for each cylinder, low in-engine friction losses, sophisticated turbocharger technology, highly resistant materials and full electronic control. Mercedes-Benz was the first brand to introduce the latter as long ago as 1996.

A sophisticated powertrain with suitably geared transmissions and drive axles with low friction losses lead to further savings. The current generation of automated Mercedes Power Shift transmissions in Mercedes-Benz trucks helps to ensure very low fuel consumption figures. Even highly experienced drivers are now unable to better these by manual operation.

The touring coaches and inter-urban buses of Daimler's Mercedes-Benz and Setra brands benefit from this highly developed engine technology and the skilled configuration of the entire powertrain. They too save both their operators and the general public enormous quantities of fuel each year. The latest example is the introduction of engines complying with exhaust emission standard Euro 5 for almost all variants of the touring coaches and inter-urban buses at the end of 2007/beginning of 2008. This is well before Euro 5 becomes mandatory in the autumn of 2008/9.

Another contribution to fuel economy and the conservation of resources is made by the new, automated eight-speed Mercedes-Benz GO 240-8 PowerShift manual trans­mission which is available specially for touring coaches from spring 2008 .

With regard to emissions, regular-service city buses operate in particularly sensitive areas. For this reason Mercedes-Benz not only supplies the Citaro city bus to Euro 5 specification, but also according to the even more stringent, voluntary EEV ex­haust emission standard (EEV = En­hanced Environmentally Friendly Vehicle). In this case engines with BlueTec tech­nology are also equipped with a downstream particulate filter.

Environmental protection has a particularly high priority for public transport operators. Daimler Buses not only supports them in their procurement of new vehicles by offering low-emission vehicles: city and inter-urban buses meeting exhaust emission standard Euro 3, and in part also buses with Euro 2, can be retrofitted with a particulate filter. The result of this strategy is that roughly two thirds of the regular-service city buses now operating in Germany are already equipped with a particulate filter.

The automatic transmissions used in regular-service city buses play an important part in the reduction of fuel consumption. The deciding factor is sophisticated con­trol of the shift programmes. Depending on the topographical characteristics of an individual route, the latest transmissions in the Mercedes-Benz Citaro are able to select the currently most suitable shift programme from several programmed into the transmission.

With due regard to local conditions, Daimler Trucks is just as committed to environ­mental compatibility and economy on other continents. One specific example is the very recently introduced, all-new DD 15 engine generation from Detroit Diesel – the first member of the new HDEP engine family. These units will initially be used in Freightliner trucks, and are in-line six-cylinder engines initially with a displacement of 14.8 litres featuring high-pressure common-rail injection, turbocompound tech­nology and a market-specific combi­nation of exhaust gas recirculation and a parti­culate filter. This first representative of the new Heavy-Duty Engine Platform from Daimler Trucks meets the North American exhaust emission standard EPA 07. The new DD 15 has the potential to meet future emission regulations on all continents.

The development of this series demonstrates the advantages of the worldwide Daimler Trucks network, for not only American but also European and Asian engi­neers were involved in the development of the new engine platform. This also made it possible to develop a new diesel engine for heavy trucks by Mitsubishi Fuso on the same platform at the same time. Its technology is basically the same as the DD 15, however its configuration and peripheral units are tailor-made for Japanese requirements, for example the current exhaust emission standard JP 05. The new DD 15 replaces the DD 60, which has been the best-selling heavy-duty commercial vehicle diesel engine in North America for several decades. In the 1980s the DD 60 was the first engine to feature full electronic control, a milestone in engine development.

In addition to engine and drive technology, aerodynamics also have a particularly important part to play where long-distance trucks are concerned, though there are limits to the improvements that can be made to the wind resistance of commercial vehicles owing to the necessary cargo capacity, dimensions and contours. In Europe the matter is made even more difficult by legal limitations to the overall length of trailer and semitrailer combinations. The loading length restrictions applicable in the NAFTA countries not only allow more scope for the interior design of the driver’s cab, but also for its exterior design with aerodynamic efficiency in mind. This is why Freightliner started operating a state-of-the-art wind tunnel for medium and heavy trucks in Portland/Oregon in back in 2004.

The first result is the Freightliner Cascadia newly presented this year, an aero­dynami­cally optimised Class 8 heavy-duty semitrailer tractor. 2500 hours of inten­sive work in the wind tunnel have produced a driver’s cab which offers the lowest possible wind resistance despite its size, thereby saving valuable fuel for the benefit of the operator and the environment. The measured 3% fuel saving resulting from the optimised aerodynamics means an annual reduction in fuel consumption of no less than 1500 litres of diesel.