AMSOIL vs. Harley-Davidson Oil: How We Perform

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

It’s no wonder since Harley-Davidson dominates two-wheeled culture despite the resurgence of the Indian brand and the rising popularity of adventure bikes and everything you can do with them.

The company’s founding is a great story. William Harley and Arthur Davidson built their first motorcycle in a 10×15 shed right here in our home state of Wisconsin. While the duo’s 116-cc prototype bike lacked the power to ascend the hills around Milwaukee, it turns out it had the power to reshape American culture.

That’s one reason several AMSOIL employees ride Harleys.

But, what about Harley-Davidson motorcycle oil?

To see how AMSOIL Synthetic V-Twin Motorcycle Oil performs vs. Harley-Davidson oil, check out the performance-test results for yourself.

AMSOIL vs. Harley SYN3

AMSOIL 20W-50 Synthetic V-Twin Motorcycle Oil resists viscosity breakdown 6X better that Harley-Davidson SYN3 Oil.*

Why viscosity matters

Viscosity is the most important property of a lubricant. While it’s defined as “resistance to flow,” it helps to think of viscosity as the oil’s thickness.

Your motorcycle engine, transmission and primary are designed to use oil of a specific viscosity, likely 20W-50 if you’re riding a Harley. The higher the numbers, the thicker the oil. So, a 20W-50 is thicker than the 5W-20 oil you use in your truck.

Oil that’s too thin reduces wear protection

Oil that’s too thin for its application won’t form a durable fluid film on metal components. The oil film protects the bearings from wear, helps keep the piston from scuffing against the cylinder wall, protects the transmission gears, guards against compensator wear and more.

In the transmission, for example, 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.

It’s the same story in the primary. The oil must protect the compensator from wear to prevent noise. If it doesn’t, you’ll find yourself on your phone reading the glut of content 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.

Avoiding this scenario seems easy enough – just use a good oil that maintains its viscosity and forms a strong, protective film on parts.

Motorcycles destroy lesser oils

That’s easier said than done.

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.

And nothing derails your pursuit of freedom on the open road like a noisy bike.

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.*

So, while we love Harley’s rich history of freedom and independence, we’ll stick with AMSOIL Synthetic V-Twin Motorcycle Oil over Harley-Davidson SYN3 oil.

AMSOIL V-Twin Oil Change Kit

*Based on 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.


  1. AMSOIL makes my bike run cooler and way quieter! I don’t use anything but AMSOIL in any of my vehicles…motor oil ..transmission fluid it’s far superior.

    1. I don’t believe that Mobil One is a full synthetic oil because they put it in a new motor with the rings not even seated. Do that with AMSOIL and the rings will never seat. also when change the oil the first time with AMSOIL and you start the motor and let it run for a while and then shut it off and check the oil level, it will show a half a quart low. That half a quart of oil is staying up in all of the parts that need the oil on start up therefore eliminating wear on start ups and that is a fact!!!

  2. Years ago, at AMSOIL U, I was told HD did want AMSOIL to be in their bottles, but did want AMSOIL mentioned anywhere on the bottle. The great foresight that Al possessed, made him say absolutely not! We guarantee our oil, and without our name on it, we can not, will not do that. Our integrity was on the line, and should some unscrupulous person decide to try and pull something, as some have in the past, we would have to fight not only the complainant , but HD and the entire population as well. I do believe their oil comes from Venezuela, manufactured by Citco. Please inquire if this is still correct. All I know is, once they change to AMSOIL, I have never had anyone change back, and have had many tell me how well it dropped temps and saved their bikes.

  3. Harley should have done the smart thing: partnered with and recommended Amsoil, which is clearly the BEST oil, instead of trying to make a few dollars by peddling inferior lubricants with their name on the label.

    1. Amsoil can confirm or deny this rumor, but HD wanted Amsoil to produce their HD brand of synthetic oil, but Amsoil refused to make an oil at the spec HD wanted, because it was to far below their base specs for synthetic oil.

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