MERCEDES 1717/1720
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• The 1717 and 1720L represent both ends of the new Mercedes-Benz middleweight range which took over from the 1617 last autumn. Both models benefited from the package of revisions which accompanied that change, including an updated cab, extended servicing intervals and some detailed chassis modifications.
The 1717 takes on the turbocharged driveline unchanged from the 1617; as suggested by its designation, the 1720 gets 20% more power courtesy of charge-cooling, backed up by 14% more torque produced 100rpm further down the scale.
To suit its superior output the 1720 gets higher gearing in an attempt to produce benefits in economy as well as speed; the two trucks use the same six-speed gearbox.
Neither version could be called a lightweight. No major effort was expended on weight saving for this event — the 1720 was actually the same chassis we tested earlier this year (CM 21-27 Feb) — and the Mercedes were easily the heaviest vehicles in the group, especially the air suspended 1720L.
On the road, Mercedes' claim for the improved efficiency of the 1720 compared with the 1717 was born out. While the journey times recorded by the two trucks were extremely similar the more powerful vehicle gave a useful bonus in fuel consumption, recording an excellent 21.93/lit100km (12.89mpg) compared with 22.671it/100km (12.46mpg) from the 1717. It is interesting to note that the lower gearing in the 1717 made it as quick as the 1720 over the hills. According to our observers, this truck actually required the fewest gearchanges of the group throughout the test.
The high chassis weights ensured that the Merc pair were not in contention in the productivity stakes, but from a driver's point of view their high specification made them comfortable workplaces.
The M-type short sleeper cab provides plenty of room for pilot and mate (day or full sleeper cabs are options), and in terms of interior refinement the German trucks were arguably the pick of the crop. This was especially true of the air suspended 1720. With its relaxed cruising and sophisticated road behaviour it made a good case for itself as a long-distance mount