Automotive Oil Vs. Marine Oil

by Michael Elkins

While both automotive and marine oil can lubricate an engine, only some oils have gained endorsement by the National Marine Manufacturers Association. This endorsement assures boat operators the oil they select is up to the rigors of marine performance.


Oil lubricates the metal parts of an engine, creating a grease-wall between the engine's moving metal parts. This reduces friction, saving wear on the engine, as well as increasing energy efficiency. It also removes the chemical by-products of internal combustion, transferring them to the oil from the engine. This stands true for automotive oil and marine oil.


The NMMA has endorsed marine lubricants that meet their testing guidelines. The endorsed oils bear the TC-W3 trademark owned by NMMA for two-stroke engines, and the FC-W trademark for four-stroke engine oil. Marine oils bear the NMMA endorsement, while motor oils do not.


The primary difference between motor oil and marine oil is the NMMA endorsement or lack thereof. Endorsed marine oil has been put through specific tests to determine the appropriateness of the oil for marine use. These tests include viscosity, lubrication, foaming and rust tests. In addition, marine oil must pass a 100-hour operational test to gain any of the NMMA trademarks.

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