Designed by Rudolf Uhlenhaut to race during the 1937 Grand Prix season, this car was used by Rudolf Caracciola to win the 1937 European Championship. W125 drivers also finished in the second, third and fourth positions in the championship. The supercharged engine, with 8 cylinders in line and 5,662.85 cc, attained an output of up to 595 horse power in race trim. Knowing the 1938 engine capacity of supercharged Grand Prix cars was to be limited to 3000 cc this car was built exclusively for the 1938 season using unlimited resources and massive expenditure. The W125 was the most powerful race car ever built for about 3 decades – until large capacity US-built V8 engines in CanAm sport cars reached similar power in the mid-1960s. In Formula One racing itself, the figure was not exceeded until the early 1980s, with the appearance of turbo-charged engines in Formula One. The W125 reached race speeds of well over 300 km/h (190 mph) in 1937 on the AVUS in Berlin, equipped with a streamlined body. In land speed record runs, a Mercedes-Benz W125 Rekordwagen was clocked at 432.7 km/h (268.9 mph) over a mile and a kilometre. This car was fitted with a DAB V12 engine of 5,576.75 cc with a power of 726 BHP at 5,800 rpm. The engine caused the car to weigh over the 750 kg maximum limit, so it never appeared in Grand Prix.