What does FC-W Mean?

FC-W means Four-stroke Cycle - Water cooled motor oil.  With the ever increasing number of four stroke powered boats and water craft, the industry saw the need for motor oils to meet the requirements placed on marine engines, which are vastly different than the engines in automotive applications.  New standards were developed for viscosity and corrosion resistance, along with improved resistance to filter plugging, foaming, and aeration encountered with high load, high rpm marine motors.