50 Years of ITOY – 1990 Mercedes-Benz SK

The 18-month qualification period brought the Mercedes-Benz Schwere Klasse – Heavy Class – back into contention in 1990, with the German manufacturer prevailing over the unlucky Italians who took both second and third spots with the Iveco TurboDaily and TurboStar 480 respectively.

The SK range was a substantially new design with new engines, gearboxes and frames being matched to a re-vamped version of the previous generation’s NG cab.

The redesigned chassis was a high tensile steel design with central lubrication which remained without flitching except when offered for off-highway applications. The cab, whilst bearing a close resemblance to its predecessor, was immediately identifiable by the sloping window line of the doors and the greater use of plastic, with the enlarged grille, corner shrouds, stepwells and wings all made of the material. The cabs employed galvanised steel sections and were available in five formats – day, short sleeper, full sleeper, “Grossraum” and a short cab with top sleeper – not previously offered by Mercedes.

The SK range spanned the 260hp to 480hp range and five variations of the new “440 Series” vee engines were employed across the various models. Surprisingly for the time, the 260hp and 290hp trucks were powered by the naturally aspirated OM 442 in 15-litre V8 form, whilst the turbocharged OM 442 A, 14.6-litre V8 provided 354hp, or 480hp in intercooled form designated the OM 442 LA. In the middle of the range sat the OM 441 LA, an 11-litre, intercooled V6 engine, rated at 330hp which really caught the judge’s attention. In fact, the judge’s commendation specifically referred to this model.

The new V6 engine retained the 90-degree cylinder block arrangement but featured a new crankshaft design with crankpins offset by 30 degrees so that the better-spaced firing order would give a much more smooth-running engine than the earlier Mercedes V6 units. With a revised cylinder head design and injection system, the OM 441 LA was a very compact engine in the 300hp-plus class and promised improved fuel consumption to give Mercedes a strong competitor for the likes of the Volvo FL10, and Cummins L10-powered trucks.

All SK on-highway models of 290hp-plus featured Mercedes’ own 9- or 16-speed transmissions which incorporated the pneumatic selector controls for the Electronic Power Shift, and optional anti-wheelspin and ABS completed the package.

The Mercedes also scored highly on the 45,000km chassis service intervals – courtesy of the central lubrication system – and the build quality and fit of detailed items such as electrical installations and piping, which the judges pointed out are responsible for more breakdowns than major component failures, making them of prime importance to reliability.

Text : Will Shiers Photos : Richard Stanier