The aim of Opel's second restructuring in as many years is to cut costs in Europe, where new-car sales are poised to decline for the fifth straight year in part because of the region's debt crisis.
Through April, European sales at Opel and UK-based sister brand Vauxhall were down 16 percent to 294,998 vehicles, according to data from industry association ACEA. Opel/Vauxhall's market share in Europe has dropped to 6.6 percent from 7.3 percent during the first four months of 2011.
Opel/Vauxhall accounts for the bulk of GM's European business, which reported a first-quarter operating loss of $256 million. GM Europe lost $747 million before interest and taxes in 2011 and has reported $16.4 billion in losses since 1999.
GM, the world's largest automaker, is looking to consolidate European operations to curb losses that CEO Dan Akerson has said are weighing on the company's shares.
Bochum, which produced its first Opel vehicle in 1962, has 3,100 employees, down from a peak of more than 20,100 in 1979, according to company figures.
GM said May 17 that it will move production of the next-generation Opel Astra compact to plants in Poland and the UK, raising the possibility of a shutdown of the Bochum factory. Astra output will be moved from Ruesselsheim, a plant that will remain in full use, according to the company.