In 1979, BMW teamed up with the DFVLR (German Test and Research Institute for Aviation and Spaceflight) – now known as the DLR – to convert a BMW 520/4 (E12, build year 1975) into a test vehicle. From the outside, it differed little from its petrol-powered siblings, but its four-cylinder unit burned hydrogen rather than unleaded. It didn’t take long to show that using hydrogen as a fuel in combustion engines was technically feasible.