Harley-Davidson* makes great bikes. What about their motorcycle oil?

Many bikers want to know how AMSOIL products compare to the competition, particularly against Harley-Davidson oil.

Q. What is the most important property of a lubricant?

A. Viscosity!

Why? Because the viscosity of a motor oil has to keep moving parts separated from one another to eliminate friction, heat, and wear. The ability of a motor oil to retain it’s viscosity is vital to providing excellent engine protection. While viscosity is defined as “resistance to flow,” one can think of it as the oil’s thickness. A motor oil has to provide a fluid film to separate moving parts. It has to be thick enough to absorb shock-loading in the engine and other components.

A motor oil that’s too thin (lower viscosity) for its application won’t form a durable fluid film on and between metal components. The oil film has to protect bearings from wear, keep the pistons from scuffing against the cylinder wall, protect the transmission gears, and guard against compensator wear.

In the transmission, the oil must be thick enough to develop a strong fluid film to cushion the gears against shock-loading and quiet loud “thunks.” This promotes smooth, quiet shifts.

In the primary, the oil must protect the compensator from wear to prevent noise. If it doesn’t, you’ll be trying to find out about Harley compensator noise and how to fix it. (The compensator acts like a shock absorber between the engine and transmission, helping prevent engine vibration from interfering with the transmission. When it wears out, it makes a ticking or knocking noise).

But the internal pressures and shock-loading in a motorcycle engine and other components can destroy lesser oils. Motorcycle engines, transmissions and primaries can be brutal environments that take a toll on oil. The mechanical shearing action of metal parts churning at thousands of rpm (particularly transmission gears) combined with extreme heat can cause oil to lose viscosity and become thinner.

Oil that’s too thin reduces wear protection and can lead to “thunking” transmission gears and a noisy compensator.

To help avoid these problems, use a motorcycle oil that maintains its protective viscosity, like AMSOIL 20W-50 Synthetic V-Twin Motorcycle Oil. Compared to Harley-Davidson SYN3 oil, it resists viscosity breakdown 6X better for improved protection against compensator and transmission gear wear.**

*All trademarked names and images are the property of their respective owners and may be resgistered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use.

**Based on independent testing of AMSOIL 20W-50 Synthetic V-Twin Motorcycle Oil purchased on 3/19/19 and Harley-Davidson Screamin’ Eagle SYN3 purchased on 3/19/19 in the CEC L45-KRL, ASTM D445 test.