Because GM has different brands in different countries, but use similar bodies and power trains.. Hurray for marketing?
Vauxhall was a British company wich produced cars since the 1900-s. Then 1925 they were bought by GM. The real "Opelesation" of the cars started in the 60-70-s. Those days Opel designed cars were built in England (some still are). And quite frankly you don't change the name of a well known and well bought brand do you?
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