AMSOIL Synthetic 10W-40 Dirt Bike OilA Synthetic 10W-40 Dirt Bike Oil is specifically designed to withstand the rigors of motocross racing, dirt biking and trail riding. AMSOIL Dirt Bike 10W-40 maximizes performance and improves engine, transmission and clutch dependability.

AMSOIL 10W-40 Synthetic Dirt Bike Oil package sizes include:

  • Single US Quart Bottle
  • Case of 12 US Quart Bottles

We can offer AMSOIL Synthetic 10W-40 Dirt Bike Oil at the lowest prices in Canada or the US. Request a wholesale price list using the contact form on this page.

About AMSOIL Synthetic 10W-40 Dirt Bike Oil

Off-road and motocross bikes are often exposed to high-stress conditions such as deep mud or sand, high RPM and extreme heat. AMSOIL designed this oil to protect engines and transmissions and to also deliver steady wet-clutch operation and shifting. Clutches can fade after a several practice starts and can fail altogether after a muddy 20 minute moto. AMSOIL Dirt Bike 10W-40 is a dedicated four-stroke engine and transmission oil that combats the all of the specific issues unique to off-road motorcycles.

Fights Clutch Fade and Clutch Plate Failure

The hallmark of this Synthetic 10W-40 Dirt Bike Oil is the prevention of clutch fade for consistent wet-clutch engagement. Dirt Bike clutches are susceptible to damage due to situations like long delays for the starting gate to drop, muddy or sandy conditions or exceptionally hard racing. Some riders simply slip their clutch more than others. The unique frictional properties of this oil formula fights heat so fiber clutch plates do not expand or warp. The result is consistent clutch lever feedback and maximum power put to the rear wheel where it belongs.

Clutch plates using AMSOIL Dirt Bike Oil

Eli Tomac Powers Through Mud

AMSOIL 10W-40 Synthetic Dirt Bike Oil is the exact oil used by the Geico Honda race team. (photo credit:

Serious Gear Protection and Smoother Shifts

Motocross bikes and other dirt bikes are subjected to relentless gear mashing virtually every time out. AMSOIL Synthetic 10W-40 Dirt Bike Oil is designed to prevent metal-to-metal gear damage from hard shifts. This oil also resists viscosity loss and “shear down” making it ideal for 4-stroke and 2-stroke transmissions. This synthetic formula also provides the smoothest possible shifting and is a performance upgrade over most other motorcycle oils.

Resists Heat

Dirt Bikes of all stripes are meant to be pushed to the limit. The synthetic makeup of this Dirt Bike 10W-40 reduces friction and dissipates heat, so engines, clutches and transmissions are better equipped to withstand extreme heat and hard riding, even in professional motocross races.

The Bottom Line: Optimized Performance and Improved Reliability

AMSOIL Synthetic 10W-40 Dirt Bike Oil maximizes performance and does its part to deliver the best possible lap times by reducing friction, optimizing clutch and transmission operation and reducing wear for DNF prevention.

The Same Formula Used By the Pros

AMSOIL is one of the main sponsors of the Geico Honda professional motocross team. AMSOIL takes pride in using the same formula in the pro’s bikes that we can all buy off the shelf. The AMSOIL Synthetic 10W-40 Dirt Bike Oil is designed to withstand the abuse doled by professional motocross racers, so you can rest assured that it will provide great service in your bike too.

Suitable Applications for AMSOIL Synthetic 10W-40 Dirt Bike Oil

This product is suitable for any 4-stroke motorcycle engine/transmission or two-stroke motorcycle transmission requiring 10W-40 motorcycle oil. This product is ideal for motorcycles requiring the JASO MA specification. Suitable brands include Honda, Suzuki, Yamaha, Kawasaki and more. This oil is also ideal for motorcycle road racing where resistance to clutch fade is desired.

AMSOIL Dirt Bike 10W-40 is perfect for the following off-road disciplines:

  • Motocross
  • Trail Riding
  • Desert Racing
  • Cross Country
  • Enduro
  • Supermoto
  • Flat Track
  • Speedway
  • Trials
  • Road Racing

Service Life of AMSOIL Synthetic 10W-40 Dirt Bike Oil

This 10W-40 Dirt Bike Oil should be changed at the interval prescribed by your owner’s manual.


AMSOIL 10W-40 Synthetic Dirt Bike Oil (DB-40)

Kinematic Viscosity @ 100°C, cSt (ASTM D-445)14.2
Kinematic Viscosity @ 40°C, cSt (ASTM D-445)93.5
Viscosity Index (ASTM D-2270)156
Noack Volatility, % weight loss (g/100g) (ASTM D-5800)4.0
Pour Point °C (°F) (ASTM D-97)-44 (-47)
Flash Point °C (°F) (ASTM D-92)254 (489)
High Temperature/High Shear Viscosity @ 150°C , 1.0 x 106 s-1), cP (ASTM D5481)4.1
AMSOIL Synthetic 10W-40 Dirt Bike Oil
A synthetic 10W-40 oil for 4-stroke dirt bike engines and two-stroke motorcycle transmissions.
Manufacturer: AMSOIL
Model: Synthetic 10W-40 Dirt Bike Oil
Product ID: DB-40