It doesn't give them more power. As I understand it, small planes last a long time, and a lot of them have old engines that were designed for leaded gas and we

It doesn't give them more power. As I understand it, small planes last a long time, and a lot of them have old engines that were designed for leaded gas and wear out faster if run on unleaded fuel. Thus, the FAA is reluctant to approve unleaded fuel in those aircraft.