Based upon the legendary W194 sports racer, Mercedes-Benz introduced the production 300SL in New York in 1954. The US was expected to be its primary market, and Mercedes-Benz importer Max Hoffman had encouradged Mercedes-Benz managment to build it. During the 300SL’s life three out of four were sold in the US. There were only 1858 SL Roadsters ever produced.
Built only in its Gullwing coupe configuration from 1945 through 1956, it was supplanted in 1957 by a convertible called the Roadster by Mercedes-Benz, in spite of its roll-up windows and well-scalled convertible top.
The 300SL roadster was vastly improved. The multitube chassis was redesigned with lower sills for easier entry and exit and conventionally hinged doors. The roll-up windows overcame on the Gullwing’s greatest drabacks: inadequate interior ventilation.
Built completely with steel except for the aluminium bonnet (hood), doors and boot (trunk), the 300SL could have been ordered with an all-aluminium outer skin, saving 80 kg (176 lb), but at tremendous added cost.
The engine, canted at a fifty-degree angle to the left to allow for a lower hoodline, was the same 3.0 liter straight-6 as the regular four-door 300 but with a Bosch mechanical fuel injection system that more than doubled its power from 86 kW (115 hp) in its original carbureted trim to 180 kW (240 hp) at 6100 rpm.
This new injection system, a first in any gasoline-powered car (apart from the rather small Gutbrodt where the Mercedes engineers had to work after the war), allowed a top speed of 260 km/h (161 mph) depending on gear ratio (several options), making the 300SL the fastest production car of its time.
The maintenance requirements were high as, unlike the current electrically powered fuel injection systems, the mechanical fuel pump would continue to inject gasoline into the engine during the interval between shutting off the ignition and the engine’s coming to a stop; this gasoline was of course not burned, and washed the oil from the cylinder walls and ended up diluting the engine’s lubricating oil, particularly if the engine was not driven hard enough nor long enough to reach a temperature high enough to evaporate it out of the oil.
Aerodynamics played an important role in the car’s speed. Mercedes-Benz engineers even went so far as to place horizontal "eyebrows" over the wheel openings.
Given the car’s overall styling, it has been suggested that the eyebrows were added to make the car more appealing to American buyers rather than to serve any functional purpose since American cars of the period were rather flamboyant by comparison to the 300SL. Unlike many cars of the 1950s, the steering was rather precise and the four-wheel independent suspension allowed for a reasonably comfortable ride and markedly better overall handling. However, the rear swing axle, jointed only at the differential, not at the wheels themselves, could be treacherous at high speeds or on imperfect roads due to extreme changes in camber.