AMSOIL vs SYN3: Which Synthetic Oil is Better for Your Motorcycle?

If you own a motorcycle, you know how important it is to use the right oil for your engine. Synthetic oils are designed to provide superior performance, protection and durability compared to conventional oils. But not all synthetic oils are created equal. In this article, we will compare two popular brands of synthetic oil for motorcycles: AMSOIL and SYN3.

AMSOIL is a pioneer in the synthetic oil industry, having introduced the first API-qualified synthetic motor oil in 1972. AMSOIL offers a wide range of products for different applications, including motorcycles, cars, trucks, boats, snowmobiles and more. AMSOIL claims to have the most advanced synthetic oil technology in the world, with superior wear protection, extreme temperature resistance, fuel efficiency and engine cleanliness.

SYN3 is a synthetic oil developed by Harley-Davidson for its own motorcycles. SYN3 is formulated to meet the specific needs of Harley-Davidson engines, which operate at higher temperatures and pressures than most other motorcycles. SYN3 claims to provide excellent lubrication, cooling, corrosion protection and noise reduction for Harley-Davidson engines.

So how do these two synthetic oils compare? Let’s look at some of the key factors that affect the performance and quality of synthetic oils.


Viscosity is a measure of how thick or thin an oil is. It affects how well an oil flows and lubricates the engine parts. The viscosity of an oil is indicated by its SAE grade, such as 10W-40 or 20W-50. The lower the number before the W, the better the oil flows in cold temperatures. The higher the number after the W, the better the oil resists thinning in hot temperatures.

AMSOIL offers a variety of viscosity grades for motorcycles, ranging from 0W-40 to 20W-50. AMSOIL recommends using the viscosity grade that matches the manufacturer’s specifications for your motorcycle. AMSOIL also claims that its synthetic oils have a higher viscosity index than conventional oils, which means they maintain their viscosity better across a wide range of temperatures.

SYN3 has only one viscosity grade: 20W-50. This means that SYN3 is designed to work well in both cold and hot temperatures, but it may not be optimal for all motorcycles. SYN3 also claims to have a high viscosity index, but it does not provide any data to support this claim.


Additives are substances that are added to an oil to enhance its properties or prevent problems. Some of the common additives used in synthetic oils are detergents, dispersants, antioxidants, anti-wear agents, friction modifiers and viscosity improvers. Additives play a vital role in protecting the engine from wear, corrosion, deposits, sludge and oxidation.

AMSOIL uses a proprietary blend of additives that are tailored to each product and application. AMSOIL claims that its additives are carefully selected and balanced to provide maximum performance and protection for each type of engine. AMSOIL also claims that its additives are more stable and effective than those used in conventional oils.

SYN3 does not disclose the specific additives that are used in its formulation. SYN3 only states that it uses “a specially formulated additive package” that meets or exceeds Harley-Davidson’s specifications. SYN3 also states that it is compatible with other Harley-Davidson oils and lubricants.


Performance is the ultimate test of how well an oil works in an engine. Performance can be measured by various factors, such as engine power, fuel economy, wear protection, engine cleanliness and service life.

AMSOIL has conducted several tests and studies to demonstrate the performance of its synthetic oils compared to conventional oils and other synthetic oils. Some of these tests include:

  • The Four-Ball Wear Test, which measures the wear scar diameter on four metal balls under high pressure and temperature.
  • The NOACK Volatility Test, which measures the percentage of oil that evaporates under high temperature.
  • The Sequence IIIG Engine Test, which measures piston deposits, oil consumption and wear in a gasoline engine.
  • The Kurt Orbahn Shear Stability Test, which measures the change in viscosity of an oil after being sheared by a high-speed metal device.
  • The Falex Pin and Vee Block Test, which measures the load-carrying capacity and extreme pressure protection of an oil.

According to these tests, AMSOIL synthetic oils outperform conventional oils and other synthetic oils in terms of wear protection, volatility, engine cleanliness and shear stability. AMSOIL also claims that its synthetic oils can extend the drain intervals up to three times longer than conventional oils or other synthetic oils.

SYN3 has not conducted any independent tests or studies to compare its performance with other oils. SYN3 only relies on Harley-Davidson’s own testing and certification process, which is not publicly available or verified by third parties. SYN3 also does not provide any data or evidence to support its claims of superior performance and protection.


Based on the information available, AMSOIL and SYN3 are both synthetic oils that are designed for motorcycles, but they have some significant differences in terms of viscosity, additives and performance. AMSOIL offers a wider range of viscosity grades, a more transparent and advanced additive package, and more proven and documented performance benefits than SYN3. SYN3 has only one viscosity grade, a vague and proprietary additive package, and no independent or verifiable performance data.

The table below summarizes the main differences between AMSOIL and SYN3:

ViscosityMultiple gradesOne grade
AdditivesProprietary and transparentProprietary and vague
PerformanceTested and provenUnverified and unsupported

Ultimately, the choice of synthetic oil for your motorcycle depends on your personal preference, budget and engine requirements. However, based on the available information, AMSOIL seems to have an edge over SYN3 in terms of quality, performance and protection.