Browse Publications Technical Papers 2007-32-0079

Development of new engine oil technology designed to bring more benefits to the boat owner than passenger car motor oils can provide 2007-32-0079

Several engine manufacturers are offering 4-stroke marine engines in order to meet 1998 US EPA emissions regulations requiring a 75% hydrocarbon reduction by 2006. These 4-stroke marine engines have been lubricated with passenger car motor oil in the past; however, the environment in which these engines operate is quite different from a passenger car engine. Perhaps the biggest differences are that marine engines do not use a closed loop cooling system, and they often operate in a corrosive salt water environment. They may be operated for extended periods of time at low speed while trolling, allowing build-up of water and fuel in the engine oil. For these reasons, oil used in this application should have corrosion inhibiting properties that are much better than what is found in passenger car oil. In addition, boats are often used seasonally and stored for long periods of time during the winter. This can lead to corrosion during storage, and require long lasting corrosion protection from the engine oil. Another area of concern about using passenger car oils is wear protection. It is common to go from idle to full throttle quickly and often, placing a sudden heavy load on these engines. The new American Petroleum Institute (API) categories for passenger car motor oils have focused on reducing emissions. The emissions reductions have been accomplished by lowering the percent phosphorous in the engine oils because its has been found to poison the catalyst in the catalytic converter. These phosphorous reductions had to be made without compromising wear protection in automotive engines. However, in marine applications, hydrolysis of the ZDP may occur, reducing the effectiveness of these antiwear agents. These lubricant concerns led the National Marine Manufacturers Association (NMMA) to develop the FC-W® (Four-Cycle Watercooled) oil specification, which was launched in August 2004. This paper focuses on developing engine oil technology with enhanced corrosion and wear performance to meet the requirements of 4-stroke water cooled marine engines.


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