U4.4 REGIf youre not bound by fuel rules this leaded fuel is the best choice for virtually any powersports application. U4. 4 reg offering the biggest gain vs. cost of any performance part you can buy. The latest generation of our U4 based fuels U4. 4 Reg makes more power than pump fuel across a wider range of applications than its predecessors. Designed as a direct pour in replacement for pump fuel it will require modest jetting changes i. e. +2 main jets or