The Gendarme and the Creatures from Outer Space (1979) on Netflix

Plot summary

Out on the road with one of his gendarmes, Ludovic Cruchot has to stop to fix the car, and his man wanders into a field and sees a flying saucer, which flies away. The gendarme tells Cruchot and the station, and they do not believe him. Cruchot then sees the saucer himself, and the chief of the gendarmes does not believe him either. Later, at the office, a young man appears and tells the same gendarme that he belongs to an alien expedition that has come to Saint-Tropez to examine humanity, since people from all around the world go there in summer. The young man takes the gendarme's own appearance, and the gendarme runs to tell Cruchot, who does not believe him. The visitors drink machine oil, and a metallic sound gives them away.