Wandering around what we seem to remember as the basement of the Frankfurt Auto Show revealed this Mercedes C111 Rekordwagen. The five-cylinder diesel propelled this C111-IID research vehicle to an average speed of 252 km/hr at the test track at Nardo, Italy. The crew set a total of 16 world records in the process. The first versions of the C111 test platform were powered by a wankel engine, which Mercedes engineers ultimately determined to be too inefficient by design. They opted instead for the precision of a turbodiesel.