Engines: Synthetic Oil

Synthetic oil is available for both four-stroke and two-stroke marine engines. Because marine engines operate under high load and at a high rpm for extended periods, it is critical to choose a marine-rated synthetic oil.

The National Marine Manufacturers Association sets standards for marine oil in its FC-W and TC-W3 specifications (FC – four cycle; TC – two cycle and W indicates its formulated to tolerate water contamination.

Synthetic gear case oil is also available for outboard and stern-drive marine engines. It provides extra rust and wear protection for the gears, improves power output and fuel economy.

The main disadvantage of synthetic oil is that it costs two to three times more than conventional oil. However, extended engine life more than offsets the higher price.

When marine engines site idle at dockside (or on a trailer), there may be a problem with acids in suspension in the motor oil to attack cylinder walls. However, synthetic oils include additives that neutralize crankcase acids, providing protection superior to conventional motor oil.

(ed: You will have to determine whether or not synthetic oil, as well as synthetic gear case oil, makes sense for your boat engine based upon how much you use your boat. Check with your marine mechanic and other boaters).

Reasons to Use Synthetic Oil:
Longer engine life
Improved fuel economy
Easier cold starts
Cooler running (5 to 20 degrees cooler)
Reduced engine deposits
More horsepower
Extended change intervals (4 to 8 times longer than regular oil)

Source: “MotorBoating” magazine: http://www.motorboating.com/articleHtml.jsp?ID=1000068534