AMSOIL 10W-40 100% SYNTHETIC DIRT BIKE OIL

AMSOIL 10W-40 100% Synthetic Dirt Bike Oil is purpose-built for the unique demands of off-road motorcycle engines, transmissions, and wet clutches. It delivers consistent clutch engagement, strong wear protection, and thermal stability in a single formulation designed around real-world rider feedback and lab testing.

Dirt bikes operate under conditions that destroy ordinary motor oils. High-rpm four-stroke engines share oil with the transmission and wet clutch, meaning the lubricant has to protect gears and bearings while still delivering predictable clutch feel. Add the extreme heat generated during aggressive riding, roost-throwing starts, and prolonged low-speed technical sections, and you have an environment that demands a purpose-formulated synthetic dirt bike oil.

CONSISTENT CLUTCH FEEL FROM START TO FINISH
Clutch fade and inconsistent lever feel are more than an annoyance. On a holeshot or a tight switchback climb, unpredictable clutch engagement can cost a position or put you on the ground. AMSOIL 10W-40 Synthetic Dirt Bike Oil is engineered with superior friction-durability properties that minimize clutch slippage, fade, and chatter. In an extreme simulated-start test, AMSOIL continued to deliver consistent clutch feel after 32 simulated race starts. A leading OEM-branded oil showed inconsistent clutch-lever action and poor engagement after only 16 starts. The clutch plates lubricated with AMSOIL remained clean and in good overall condition, while the OEM oil plates showed visible discoloration and wear.

PROTECTS GEARS, BEARINGS, AND PISTONS AGAINST WEAR
A dirt bike engine oil has to do triple duty. It lubricates the engine, cools internal components, and protects the transmission gears, all from the same sump. AMSOIL Synthetic Dirt Bike Oil uses synthetic base oils that naturally resist mechanical shear and viscosity loss under high-rpm operation and extreme heat. That thick protective film stays intact where it matters, preventing metal-to-metal contact across gears, bearings, and piston surfaces. Premium anti-wear additives provide an additional layer of defense. In Four-Ball Wear Testing (ASTM D4172, 40 kgf, 150°C, 1800 rpm, 1 hr), the 10W-40 formulation produced a wear scar of just 0.57 mm.

RESISTS HEAT AND VISCOSITY BREAKDOWN
Air-cooled and liquid-cooled dirt bike engines both generate punishing heat, especially during slow-speed technical riding where airflow drops off. Oil that thins out under heat and shear leaves critical components exposed. AMSOIL 10W-40 Dirt Bike Oil posts a NOACK Volatility result of just 4.8% weight loss (ASTM D5800) and a High-Temperature/High-Shear Viscosity of 4.0 cP at 150°C (ASTM D5481). These numbers reflect a formulation that holds its viscosity grade and protective film strength when operating temperatures climb.

MAXIMIZES HORSEPOWER DELIVERY
Every bit of power matters on a 450 or even a 250. Oil that causes excessive drag in the clutch pack or transmission robs horsepower that should be going to the rear wheel. AMSOIL Synthetic Dirt Bike Oil is formulated to reduce frictional losses without compromising clutch engagement, helping maximize the power your engine actually puts to the ground. The formulation was fine-tuned using a combination of professional racer feedback and laboratory testing, balancing wear protection and clutch performance against power delivery.

EXTENDS CLUTCH AND ENGINE LIFE
Clutch plate replacement is one of the most common maintenance items on hard-ridden dirt bikes. Oil that glazes or wears clutch friction surfaces accelerates the replacement cycle. AMSOIL's simulated-start testing demonstrated clean, undamaged clutch plates after 32 starts, compared to discoloration and wear on the OEM oil plates at just 16 starts. That translates directly to longer clutch life and fewer rebuilds over the course of a season. The same anti-wear chemistry that protects clutch plates also reduces gear and bearing wear, helping extend overall engine service life.

SPECIFICATIONS AND COMPATIBILITY
AMSOIL 10W-40 Synthetic Dirt Bike Oil meets JASO MA and API SG, SJ, SH, SL specifications. It is recommended for dirt bikes requiring 10W-40 motorcycle oil from Honda, Yamaha, Kawasaki, Suzuki, and Husqvarna. This includes separate-sump applications like the Honda CRF series and many two-stroke dirt bikes that use 10W-40 in the transmission. It is compatible with other synthetic and conventional motor oils, though mixing will reduce the performance benefits and life expectancy of the AMSOIL product. Aftermarket oil additives are not recommended.

SERVICE LIFE
AMSOIL Synthetic Dirt Bike Oil should be changed according to the vehicle manufacturer's recommendations.