A new liquid cooled gasoline powered aircraft piston engine has been introduced to the General Aviation marketplace. To achieve additional benefits of liquid cooling, higher coolant operating temperatures are incorporated. Initial aircraft operating experience with the initially selected commercial ethylene glycol based coolant using traditional inhibitor packages resulted in excessive radiator core plugging.A program was initiated to determine the cause for the radiator plugging and identify solutions. Another commercially available ethylene glycol based coolant with a revised inhibitor package was selected as a promising solution. Evaluation of the coolant has been conducted resulting in significantly reduced deposit formation.