Diesel is still sweeping Europe. Hybrids are catching on in North America and Japan. But these trends are only short-term, as the industry prepares for the day the world’s fuel reserves dry up, some auto engineers said at the 75th International Motor Show in Geneva.

Nearly every automaker is here showing off its latest hybrid cars, fuel cell models or electric prototypes, along with the latest diesel options. “Diesel is popular in Europe, clearly, but it’s a short-term trend,” said Laurent Aebi, a product specialist at Honda Motor Co., which was displaying its new FCX fuel cell car, powered by an electric motor that uses hydrogen as its energy source. “I give it another 10 years maximum. After that it will be the hybrid car. But both the diesel car and hybrid car are a transition as we head to fuel cell cars or pure electric cars.”