Total Production: 1,201 1936 - 1938 The 25/30 was an improvement on the 20/25 and ultimately marked the final development of the Twenty. The engine was enlarged to 4,257 cc and although similar in looks to its predecessor it was highly regarded, (a 25/30 can be distinguished from a late 20/25 by its three-spoke steering wheel). 1,201 25/30s were sold in just two years of production.
Some significant changes had been made for the 20/25, the most obvious being the use of proprietary parts. These included a Stromberg carburetor, SU fuel pumps, Lucas electrics, a Borg and Beck clutch, Marles steering and a Hardy Spicer propeller shaft.
The use of parts manufactured by other companies helped Rolls-Royce get to grips with the rising costs of manufacture. It was Henry Royce's financial pursuit for perfection that had precluded the use of proprietary parts in the past, but following his death in 1933 their use became more widespread. Until that time Rolls-Royce was about the only car company in the world to manufacture its own electrical, equipment. This practice was later described as the 'Silver Ghost mentality', but it was clear that the manufacturing process had to become modernized in order for the company to remain competitive.Source - Rolls-Royce Motor Cars Ltd.