Nissan and Renault are extending their partnership by working more closely in four areas – R&D, manufacturing and logistics, purchasing and human resources.
The aim is to save £3.7bn a year by 2016 by "accelerating synergies" between the two companies.
Carlos Ghosn, chief executive of both carmakers, told the Financial Times: "In our industry, a big part of competition is scale. If you do not have scale, then you cannot be competitive. So it is logical."
Manufacturing and logistics projects will focus on how to improve plant performance through more rigorous benchmarking. The teams will also review how to optimize capital expenditures through standardization, better capacity utilization and logistics efficiency.
Renault and Nissan will also study how to allocate research on next-generation technologies to spread resources further. The R&D study will also focus on the acceleration of common platforms, define and deploy a common powertrain strategy, and optimize test facilities globally.
Renault owns just over 43% of Nissan, which in turn holds 15% of the French carmaker.