Motorcycles, Dirt Bikes And ATVs/UTVs Have Unique Needs

No Oil Is “One-Size-Fits-All.”


Whether in an air-cooled V-twin, metric sport bike, hard-working UTV or professional dirt bike, oil has to protect against wear and fight the damaging effects of extreme heat. Years ago it was possible to make one motor oil to protect all these applications. But today’s engines aren’t so simple.

V-Twin Motorcycles

Air-cooled V-twins can get hot. In our dyno testing of a 2019 Harley-Davidson* Milwaukee-Eight* engine, the rear cylinder temperature hit 421°F (216°C).

  • August 2018 You Tube of Dyno Test (This link added by SLS Associates)
  • 2019 Street Bob You Tube Test Results (This link added by SLS Associates)

Heat that intense can wreak havoc on the motor oil. The oil can lose viscosity and become thinner. A lighter viscosity than what the engine is designed to use can fail to protect parts against wear. Extreme heat also hastens chemical breakdown. In fact, the rate of oxidation doubles for every 18°F (10°C) increase in oil temperature.

It’s vital that the oil meant for your air-cooled V-twin is formulated to withstand such intense heat. To accomplish that, we formulate AMSOIL Synthetic V-Twin Motorcycle Oil with added resistance to extreme heat. Its naturally heat-resistant synthetic base oils maintain viscosity despite extreme heat and the shearing force of transmission gears “cutting” the oil’s molecular structure. That translates into reliable protection in the toughest riding conditions.

Metric Motorcycles

In metric sport bikes, foam is one of the biggest challenges to oil. A metric bike can easily surpass 10,000 rpm. The mechanical action of the crankshaft spinning that fast can whip air into the oil, causing foam.

If the oil isn’t formulated to quickly release air, foam bubbles will travel throughout the engine, When they collapse between meshing gears or bearing surfaces, nothing is left behind to provide protection except air, We all need air, but it’s worthless at protecting high-performance engines against wear,

For that reason, we formulate AMSOIL Synthetic Metric Motorcycle Oil specifically to resist foam, Its anti-foam additives weaken the surface tension of air bubbles, helping eliminate foam. This results in excellent wear protection no matter how heavy you lay into the throttle.


Because ATVs and UTVs are often used to perform heavy work at slow speeds, oil film strength is especially important.

Slow, methodical operation when heavily loaded places increased stress on the engine bearings. If the oil’s film strength doesn’t hold up, the increased pressure will rupture the oil film and slowly wear out the bearings.

AMSOIL Synthetic ATV/UTV Motor Oil is engineered with robust synthetic base oils that allow formation of a durable protective film in the toughest conditions.

You might think, “Sure, but my Harley runs hard, too.” True, but motorcycles are typically ridden recreationally, meaning they undergo increased stress when accelerating, but level out once you reach cruising speed. Riding at a consistent speed under light load creates less stress than, for example, pulling a stump out of the ground with your UTV or pulling a loaded trailer uphill through the mud with your ATV.

Dirt Bikes

Finally, we have dirt bikes, which undergo low-speed stress punctuated with periods of high revving.

Racers lean on the throttle out of the gate, then back off into the first corner. They’re back on the throttle through the whoops, causing the rear tire to spin freely when it’s in the air. Hitting the ground, though, places a heavy load on the engine.

Where dirt bikes differ, however, is in engine design. They are typically lightweight and meant for performance. Any time you remove mass, yet increase power, you increase engine stress. The combination of high rpm and lighter materials creates the perfect scenario for engine failure should the motor oil fail to do its job. Plus, dirt bikes can produce 50 hp or more, yet they barely hold a quart of oil, exposing the oil to tremendous stress.

We kept this in mind when formulating AMSOIL Synthetic Dirt Bike Oil. It resists wear and protects powerful, lightweight dirt-bike engines. It also delivers progressive, predictable clutch feel that provides strong holding power to avoid slipping.

AMSOIL V-Twin Oil Change Kits

The moral of the story is this: The days of using one oil for all your powers ports toys are long over. Today’s engines present unique demands that require specialized lubricants. Fortunately, we have a full line of products to cover you and your customers. Find what you need with our Product Guides at

AMSOIL Small Engine Oils
AMSOIL Dominator 2-Stroke Racing Oil
  • 4-Stroke Powersports Oils & Oil Change Kits
  • 4-Stroke Power Equipment Oils
  • 2-Stroke Powersports Oils
  • 2-Stroke Power Equipment Oil
AMSOIL Saber Professional 2-Stroke Oil

*All trademarked names and images are the property of their respective owners and may be registered marks in some countries. No affiliation or endorsement claim, express or implied, is made by their use. All products advertised here are developed by AMSOIL for the use in the application shown.

Reproduced With The Permission Of AMSOIL INC. All Rights Reserved.

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