BRUSSELS—The European Commission fined German carmakers Volkswagen and BMW a total of 875 million euros ($1 billion) on Thursday for colluding to curb the use of emissions cleaning technology they had developed. The case, separate to the so-called ‘Dieselgate’ scandal over software designed to cheat on vehicle emissions tests, sets a precedent by extending the application of European competition law to technical-level talks between industry players. In this case, talks held a decade ago centered on design standards for AdBlue, an additive used to cleanse nitrogen oxide from the exhaust gases produced by diesel-powered cars. “This is a first,” European Union antitrust chief Margrethe Vestager told a news conference in Brussels. “We have never had a cartel whose purpose was to restrict the use of novel technology.” Under a settlement, Volkswagen will pay a fine of 502 million euros and BMW 373 million euros. Daimler, also part of the cartel, …