ACCORDING to industry sources, the Dah Chong Hong motor group is about to part company with the General Motors-owned German marque Opel and French manufacturer Renault. The withdrawal of Opel and Renault, distributed until now by Triangle Motors and Prosperity Motors respectively, has been confirmed by sources in the Dah Chong Hong organisation and General Motors in Hongkong. According to a Dah Chong Hong manager, the Opel and Renault brands are being dropped as part of a sweeping review of the company's motor distributorships. However, according to another source, it was General Motors which made the decision to seek out a new distributor for the Opel range, in a move to try to boost sales. During the early 1960s, Opel was Hongkong's top selling marque. Dah Chong Hong has until now been the sole Hongkong agent for both Opel and Renault, in addition to its larger distributorships handling Nissan and Honda. It is understood sales of the two European makes have been disappointing, amounting to only a few hundred annually. However, despite the loss of Opel, Triangle Motors will continue to distribute the Isuzu line of commercial vehicles. But the news has been greeted with concern by Volkswagen, and its wholly-owned subsidiary Audi, also distributed in Hongkong by Dah Chong Hong, through the Harmony Motors dealership. A source close to the company said the withdrawal of Opel and Renault was causing concern at Volkswagen. It is not certain which Hongkong dealer will take over the two brands, though Swedish Motors is said to be interested in the Opel range. ''We are looking at various things and we have had discussions with various people, but that is all I can say at the moment,'' said Swedish Motors chairman, Mr Christer Agell. Last year, Mr Agell passed responsibility for the day-to-day running of his Saab distributorship to a newly-appointed managing director. to concentrate on new business opportunities.