The W 154 was designed to fulfill the regulations for the three-liter (183-cubic-inch) formula introduced in 1938. These stipulated reduced total displacement and marked the end of the 750-kg (1,650-pound) formula, which placed a limit on the vehicle weight. The W 154 won six of the nine Grand Prix races in its first season, recorded three 1-2-3 finishes and took Rudolf Caracciola to his third European championship crown.

• Cylinders V12
• Displacement 181 cu in
• Output 453 hp (333 kW)
• at engine speed 8000/min
• Top speed 177 mph