Mercedes-Benz 250 S – 300 SEL 6.3, W 108/109 series (1965 to 1972)
The new premium-class model generation consisting of the 250 S, 250 SE and 300 SE were presented in August 1965, establishing succession to the 220 Sb, 220 SEb and 300 SE fintail models.
All three models shared a body designed by Paul Bracq, whose clean lines dispensed with all fashionable excess and whose restrained elegance has timeless appeal even today. In terms of their engineering design, the new models were based to a large extent on their predecessors.
Other than the body, however, new features also included the two 2.5-liter engines, which were developed by increasing the bore and lengthening the stroke of the corresponding 2.2-liter units. Now the crankshaft was mounted on seven bearings, and an oil-water heat exchanger guaranteed improved heat load in the oil system. In the direct-injection version a six-plunger injection pump now replaced the two-plunger pump. In contrast to its predecessor model, however, the new 300 SE was no longer fitted with air suspension. Instead, as with the two 2.5-liter models, it had a hydropneumatic compensating spring on the rear axle, which replaced the familiar coil spring and ensured a constant body height regardless of the load.
In March 1966 the model range was expanded to include the 300 SEL, which had a 100-millimeter (3.9 in) longer wheelbase compared with the basic model, the extra space serving exclusively to increase legroom in the rear and the entry width of the rear doors. As with its direct predecessor with the same model designation, the new 300 SEL featured air suspension as standard. Internally the models with conventional suspension were grouped under the W 108 model series, the air-sprung 300 SEL however was given its own series with the designation W 109.
Two special variants
In 1966 and 1967 two very special variants of the 300 SEL were built in Sindelfingen, never intended for series production and specially developed for the Vatican. In June 1966 a landaulet with normal wheelbase was built, which differed from the series saloon in that it had only a single seat at the rear and a landaulet soft-top that stretched to the front edge of the rear doors. Almost a year later, in May 1967, the landaulet was joined by two identical six-seater saloons, which were built on a floor assembly that had been lengthened by 650 mm (26 in) and boasted modified rear doors as well as two folding seats in the rear. The landaulet was intended as a second vehicle for use alongside the Mercedes-Benz 600 by His Holiness himself, whereas the two Pullman saloons were to be used for transporting Vatican guests.
Production of the 250 SE and 300 SE models came to an end at the start of 1968, with the introduction of the two successor models 280 S and 280 SE in January. These differed from their predecessors only in terms of their engines and certain equipment details. The newly-developed 2.8-liter six-cylinder engine delivered 140 hp (103 kW) in the carburettor version, and 160 hp (118 kW) with direct fuel injection. Likewise from January 1968 onwards, an output-enhanced version of the injection engine giving 170 hp (125 kW) was fitted not only to the 280 SL, but also to the 300 SEL, where it replaced the 3.0-liter light-alloy engine in service to that point.