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Yachting Magazine Test of AMSOIL Products

What better way to test the protective strengths of a motor oil than by installing it in an engine directly opposite an engine using another oil, where both engines run at the same time under the same conditions.


A marine engine must take a lot of punishment. Unlike a car, a boat is not gliding along a semi-frictionless surface; it constantly battles drag. This means the engine must work harder at all times and is under a constant load. Additionally, cooler engine temperatures, excessive idling, and "loading up" can adversely affect the life of a marine engine. It stands to reason that a good oil may substantially increase a boat's service life and reduce maintenance time and costs.


Yachting Magazine installed AMSOIL Synthetic 15W-40 Heavy Duty Diesel and Marine oil, an 8" By-Pass Oil Filter, and an ASF-25 Full- Flow Oil Filter on the port engine of their Tiara 2700 "Pursuit" Sports Fisherman Boat. The starboard engine used its usual conventional brand of 15W-40 oil and filter. Both engines were 265HP Volvo gas engines.

The test used periodic oil analysis as a gauge for how much wear the two engines experienced. Experts often call oil "the lifeblood of an engine." If this is true, oil analysis is a blood test for an engine. Oil analysis measures the amount of "erosion" engine parts undergo over a period of time by pinpointing the quantities of certain elements present in the oil. Generally speaking, the greater the amount of metals, the greater the wear.

The test ran for 17 months for a total of 880 operational hours. Initial samples (#1) were taken prior to the test to determine the engines' conditions. These samples showed that each engine had similar wear-patterns and histories. Oil analysis samples in this test were drawn at the same time from each engine and analyzed by an independent lab (Analysis Maintenance labs, Inc, Illinois). The cumulative results can be seen on the raw data page. Graphs accompanying this article show the results for the last 215 hours of the test.


The test emphatically demonstrates that AMSOIL products extend the life of an engine and its oil.

During the 17 months of the test the AMSOIL Synthetic Heavy Duty Diesel and Marine Oil was changed only once after its first year and two months of service (at test's end, the AMSOIL was still well suited for use); the petroleum oil was changed two times. Despite this fact, AMSOIL consistently outperformed its conventional competition in wear-metal reduction.

Percent Total Solids (%TS): The measure of total solids in the oil, including metal fragments, intake dirt, deposits, and other particles typically associated with engine wear. Smaller figures indicate reduced wear. Results show AMSOIL reduced total solids by 66%.

Iron Wear Particles (Fe): One of the most important "indicator" wear metals. Iron particles in oil come from such sources as cylinders, liners, pistons, rings, valves, valve guides, and anti-friction bearings. Smaller figures indicate less wear. AMSOIL reduced iron particles in the oil by a total of 53% overall.

Copper Wear Particles (CU): Copper particles in the oil come from such sources as bearings, bushings, thrust washers, valve guides, and oil cooler tubes. Results show AMSOIL reduced copper particle levels by a total of 79% overall.

Aluminum Wear Particles (Al): Aluminum particles in oil come from pistons, bearings, pump vanes, and thrust washers. AMSOIL reduced aluminum particle levels by a total of 68% overall.


  1. In most cases, AMSOIL reduced engine wear by at least a factor of two over the competitors's lubricant and conventional filter. The use of AMSOIL would significantly reduce maintenance and upkeep costs.
  2. AMSIOL Synthetic 15W-40 Heavy Duty Diesel and Marine Oil lasted much longer and was in much better condition than the competition throughout the test.
  3. AMSOIL was changed once during the test; the petroleum was changed twice. AMSOIL was deemed still suitable for use after the test period; the petroleum oil required changing. This indicates AMSOIL provides for fewer oil changes, less waste oil (economically and environmentally desirable), and less time wasted changing oil.

See the raw data from which these graphs were developed.

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