AMSOIL 20W-40 100% Synthetic Motorcycle Oil

Product Details

AMSOIL 20W-40 100% Synthetic V-Twin Motorcycle Oil is a purpose-built formula for Victory and Indian motorcycles, delivering wear protection, wet-clutch compatibility, and rust defense in a single oil that handles your engine, transmission, and primary all at once.

Air-cooled V-twin engines run hot. They share oil between the engine, transmission, and wet clutch, which means the lubricant has to do three very different jobs simultaneously. Add in seasonal storage, short weekend rides, and the mechanical shearing forces of meshing gears, and you start to understand why a generic automotive oil or even a standard motorcycle oil can fall short in these applications.

EXCEPTIONAL HIGH-TEMPERATURE FILM STRENGTH
When cylinder temperatures climb, oil film thickness is the last line of defense between metal surfaces. AMSOIL 20W-40 V-Twin Motorcycle Oil delivers a High-Temperature/High-Shear (HTHS) viscosity of 4.2 cP at 150°C (ASTM D5481), well above the 3.5 cP minimum allowable standard. That additional film strength translates directly to reduced cam, piston, and bearing wear during sustained highway cruising and stop-and-go riding in summer heat. The formula also includes a heavy dose of anti-wear additives, producing a Four-Ball Wear scar of just 0.41 mm (ASTM D4172), which confirms metal-to-metal contact is being actively minimized even under extreme-pressure conditions.

SHEAR-STABLE GEAR AND CHAIN PROTECTION
Transmission gears and primary chains generate intense mechanical forces that can physically tear apart oil molecules, thinning the oil over time and leaving components vulnerable. AMSOIL 20W-40 V-Twin Motorcycle Oil is shear stable, meaning it resists viscosity loss from mechanical activity throughout the entire drain interval. It functions like a gear lube in the transmission and primary compartments without relying on extreme-pressure additives that can cause clutch slippage or glazing. For riders using a single sump to lubricate everything, that balance is critical.

SMOOTH, CONSISTENT WET-CLUTCH PERFORMANCE
Wet-clutch engagement depends entirely on the friction characteristics of the oil. Formulas designed for automotive use often contain friction modifiers that cause clutch slippage and inconsistent shifting in motorcycles. AMSOIL 20W-40 V-Twin Motorcycle Oil meets JASO MA requirements, providing the correct friction profile for positive clutch engagement, quiet shifting, and resistance to clutch glazing. Victory and Indian riders can expect confident clutch feel whether pulling away from a stop or downshifting into a corner.

SUPERIOR RUST AND CORROSION PROTECTION DURING STORAGE
Most motorcycles spend weeks or months sitting between rides, and condensation buildup inside the engine is a real problem. Rust on cylinder walls, cam lobes, and bearing surfaces leads to uncontrolled wear, compression loss, and blow-by once the bike fires up again. Standard motor oils do not inherently provide strong rust protection. AMSOIL 20W-40 V-Twin Motorcycle Oil is formulated with dedicated anti-rust agents that coat internal surfaces and resist moisture-driven corrosion during winter storage or extended periods between rides.

THERMAL STABILITY AND CLEAN OPERATION
With a flash point of 232°C (450°F) and low NOACK volatility of just 2.7% weight loss (ASTM D5800), this oil resists evaporation and thermal breakdown in the extreme heat environment of air-cooled V-twin engines. Less volatility means less oil consumption and fewer deposits. Maximum levels of oxidation inhibitors keep the oil chemistry stable over extended use, preventing sludge and carbon buildup that can clog oil passages and reduce cooling efficiency. The formula is also catalytic-converter compatible, meeting emission-system protection requirements for equipped models.

SPECIFICATIONS AND COMPATIBILITY
AMSOIL 20W-40 Synthetic V-Twin Motorcycle Oil meets JASO MA, API SM, and ILSAC GF-4 specifications. It is a direct replacement for any motorcycle requiring 20W-40 oil meeting these standards, including Victory and Indian models. The oil is compatible with conventional and other synthetic motor oils, though mixing will reduce performance benefits and void extended drain interval support. Aftermarket oil additives are not recommended.

SERVICE LIFE
For on-road use in engines and transmissions, AMSOIL 20W-40 V-Twin Motorcycle Oil provides premium protection for up to 2X the manufacturer-recommended change interval or one year, whichever comes first, when paired with an AMSOIL Ea Motorcycle Oil Filter. Use standard intervals with other filter brands. For off-road use, follow standard manufacturer-recommended intervals. For racing or modified engines, oil changes are at the owner's discretion.