The attempt was organized by the Daimler AG Truck division from Germany and took place at the Nardo Technical Centre, a testing facility for prototype cars with a 12 km (7.46 mile) circle track.
On this track, the truck, a fully loaded 40-ton, Mercedes Benz Actros, was driven in both directions for an entire week, starting on 22 of May for 24 hours a day. During this time, it stopped only to refuel, change drivers and change driving direction. The test was monitored at all times by DEKRA, an independent testing firm for trucks.
On 29 May, one week and 12,728 km (7,908.8 miles) later, the average fuel consumption of the fully loaded truck was established as being 19,44 litres per 100 km (6.88 gal per 100 miles). This is an impressive result, as most of the attending specialists estimated that other trucks under the same conditions would use between 25 and 30 litres (5.5 and 6.6 gal) average.
The Daimler engineers also pointed out that this result meant that in the field of trucks the much discussed “one litre car” was already a reality looking at the average consumption of fuel per ton on 100 km.
Source : Guinness World Records