Production of the models 250 SE and 300 SE was stopped at the beginn of 1968; as their successors in January 1968 the Types 280 S and 280 SE were presented; they were distinguished from their predecessors only by a different engine and other equipment details. The new 2.8-liter 6-cylinder engine delivered 140 hp in its carburettor version and 160 hp with fuel injection. A more powerful version of the injection engine with 170 hp was not only built into the 280 SL, but from January 1968 into the 300 SEL, too, where it replaced the former 3.0-liter light-alloy engine.
In March 1968 the 300 SEL 6.3 became top of the class of this model series. It was equipped with the V8-engine and the automatic gearbox of the 600 model so that its power was equal to that of a high-level sportscar. Its presentation at the Geneva Motor Show created a sensation, especially since there had been no hints, that a model like this was to be forthcoming. From outside, the 6.3 could only be recognised by its broader tires, double halogen headlights and additional distance beam headlights. Even though it cost over DM 10.000 more than a 300 SEL and twice as much as the 280 SE, many customers were interested in the 300 SEL 6.3, so that 6,526 units were produced.