The extremely heavy-duty Mercedes-Benz O 10000 was a replacement for the L8500 in 1935. It was the largest bus from the Mercedes-Benz stable that could offer 50 passenger seats on single deck buses and up to 80 passenger seats in case of a double-deckers.

Though it was heavy in weight at 12 tons, it would do about 65 km/hr. Only less than 250 were made and most were purchased by the Post Offices in Germany and then Austria, where they were used as mobile post offices.