Marine cooling systems will normally have copper / copper nickel tube stacks in the heat exchangers and coolers. Traditional auto coolant can be corrosive to copper.
ORGANIC (RED): AC-9 Coolant is a premium quality, organic, long life anti boil/ anti freeze coolant concentrate suitable for both heavy duty auto and marine engines.
HYBRID (BLUE): Castrol Radicool PG Premix Blue is a ready-to-use, fully formulated hybrid technology propylene glycol based engine coolant. More robust than both conventional and organic acid technology (OAT) coolants and enables use of a single product in the cooling systems of mixed fleets of heavy duty diesel engines.