AMSOIL 10W-50 100% Synthetic Dirt Bike Oil
AMSOIL 10W-50 100% Synthetic Dirt Bike Oil is the heavier, shear-stable grade in the AMSOIL Synthetic Dirt Bike Oil family, engineered for big-bore four-stroke motocross, enduro, and trail bikes whose service manual calls for an SAE 10W-50 motorcycle oil. The formula meets JASO MA, the wet-clutch friction standard for shared-sump four-stroke motorcycle engines, and carries API SG, SJ, SH, and SL service categories.
Race-tested clutch friction durability
Wet-clutch feel is the property a 450-class rider notices first, and it deteriorates fastest on a heavy-duty 10W-50 pushing gear teeth and a clutch pack at the same time. AMSOIL Synthetic Dirt Bike Oil is built around friction durability that helps eliminate clutch slippage, fade, and chatter so lever pull stays predictable through long motos and tight enduro sections. In an extreme simulated-start test, AMSOIL Synthetic Dirt Bike Oil continued to deliver consistent clutch engagement after 32 simulated race starts, while a leading OEM-branded oil showed inconsistent clutch-lever action and poor clutch engagement after only 16 starts. Clutch plates run on AMSOIL came out clean; plates run on the OEM oil showed discoloration and wear.
Wear protection for big-bore engines and transmission gears
A 450-class four-stroke shares the engine sump with a hardened transmission, so the same oil film must protect cam lobes, crankshaft and rod bearings, the cylinder, and constantly meshing gears. The synthetic base oils in AMSOIL 10W-50 100% Synthetic Dirt Bike Oil naturally resist mechanical shear and viscosity loss, maintaining a thick protective film under high-rpm operation and extreme heat. The premium anti-wear additive package returns a 0.52 mm scar in the Four-Ball Wear Test (ASTM D4172, 40 kgf, 150 degrees C, 1800 rpm, 1 hr), supporting longer gear, bearing, piston, and clutch life.
Heavier viscosity profile for hot, sustained-load riding
AMSOIL 10W-50 Synthetic Dirt Bike Oil delivers a kinematic viscosity of 18.1 cSt at 100 degrees C and 120.8 cSt at 40 degrees C (ASTM D445), with a viscosity index of 167 (ASTM D2270). High-temperature, high-shear (HTHS) viscosity measures 4.9 cP at 150 degrees C (ASTM D5481), the load-bearing range expected of a premium 10W-50 motorcycle oil that has to lubricate transmission gears in addition to engine internals.
Low volatility, high flash, and cold-flow margin
NOACK volatility (ASTM D5800) measures 4.1 percent weight loss, helping control oil consumption between changes and reducing deposit formation on pistons and ring lands. The flash point is 246 degrees C (475 degrees F) and the fire point is 272 degrees C (522 degrees F) per ASTM D92, both well above the operating temperatures of an air-cooled or liquid-cooled four-stroke top end. The pour point reaches -38 degrees C (-36 degrees F) per ASTM D97, supporting confident cold cranking before practice sessions.
JASO MA wet-clutch spec and OEM compatibility
AMSOIL 10W-50 100% Synthetic Dirt Bike Oil meets JASO MA, the friction standard developed for shared-sump four-stroke motorcycle engines, so the formula is engineered to work with the wet clutches on competition four-strokes from KTM (450, 350, and 250 SX-F and EXC-F), Husqvarna (FC and FE 450, 350, and 250), Kawasaki KX450 and KX250F, Yamaha YZ450F and YZ250F, and Suzuki RM-Z450 and RM-Z250 whose owner manual calls for an SAE 10W-50 motorcycle oil. AMSOIL 10W-50 Synthetic Dirt Bike Oil is Warranty Secure and is backed by the AMSOIL Limited Warranty.
Recommended applications and service intervals
Use AMSOIL 10W-50 100% Synthetic Dirt Bike Oil in any dirt bike whose service manual calls for SAE 10W-50 motorcycle oil, including four-stroke models made by KTM, Husqvarna, Kawasaki, Yamaha, and Suzuki. Riders whose machines specify 10W-40 should select that grade from the AMSOIL Synthetic Dirt Bike Oil family rather than substituting this 10W-50, and machines that require a thicker 10W-60 should select the matching 10W-60 grade.
- Change AMSOIL 10W-50 Synthetic Dirt Bike Oil according to the vehicle manufacturer's recommendations; race teams typically tighten the interval based on engine hours, race weekends, fuel quality, and dust exposure.
- Compatible with other synthetic and conventional motor oils; mixing shortens life expectancy and reduces performance benefits, and extended drain intervals are not supported on mixed fills.
- Aftermarket oil additives are not recommended for use with AMSOIL Synthetic Dirt Bike Oil.
- Confirm viscosity grade, JASO classification, and sump capacity for a specific dirt bike using the AMSOIL vehicle lookup guide.
Pair AMSOIL 10W-50 Synthetic Dirt Bike Oil with a fresh, OEM-spec motorcycle oil filter at every change, replace the crush washer on the drain plug, and follow the manufacturer's torque values to prevent leaks at the case and filter cover.
Typical technical properties
| Property | Value (DB50) |
|---|
| Kinematic Viscosity at 100 degrees C, cSt (ASTM D445) | 18.1 |
| Kinematic Viscosity at 40 degrees C, cSt (ASTM D445) | 120.8 |
| Viscosity Index (ASTM D2270) | 167 |
| Flash Point, degrees C (degrees F) (ASTM D92) | 246 (475) |
| Fire Point, degrees C (degrees F) (ASTM D92) | 272 (522) |
| Pour Point, degrees C (degrees F) (ASTM D97) | -38 (-36) |
| NOACK Volatility, % weight loss (ASTM D5800) | 4.1 |
| High-Temperature/High-Shear Viscosity at 150 degrees C, cP (ASTM D5481) | 4.9 |
| Four-Ball Wear Test, scar diameter, mm (40 kgf, 150 degrees C, 1800 rpm, 1 hr) | 0.52 |
| Foam Test (ASTM D5182, Sequences I, II, III) | 0/0, 20/0, 0/0 |
| Total Base Number | 7.6 |
Order AMSOIL 10W-50 100% Synthetic Dirt Bike Oil
AMSOIL 10W-50 100% Synthetic Dirt Bike Oil ships in a quart bottle (product code DB50QT-EA) and a case of twelve quarts (product code DB50QT-CA). The product is Warranty Secure, keeps the factory warranty intact when used as a high-performance replacement for vehicle manufacturer-branded products, and is backed by the AMSOIL Limited Warranty. For application match by year, make, and model, start with the AMSOIL vehicle lookup guide, and to compare 10W-40, 10W-50, and 10W-60 dirt bike grades plus 2-stroke premix options, see the AMSOIL dirt bike oil guide. Order AMSOIL 10W-50 100% Synthetic Dirt Bike Oil.
Customer reviews
Great wear protection!
I use this in all my dirt bikes. It quiets down every engine I put it in. Never had a clutch slip. I do oil changes ever 4-6hrs of moderate track riding. 2011 crf450r, '16 crf250r, '23 kx65, '22 crf50
By Josh on June 06, 2026.
Would recommend this to a friend.
Smooth as Silk
I was running MAXIMA 10-40w 4 stroke...With this 06 yz450 has a Problem from shifting from Third to Fourth when RPM\`s are high...Its common with 06,07.....But did some researching...Had a Motocross Racer suggest running AMSOIL 10w-40 weight for better low friction from Third to Fourth.....So far Hauling Ass....Thanks # 007
By William from North Carolina on May 24, 2026.
Would recommend this to a friend.
Atv
Fantastic oil my Honda ATV ran so smoothly after using this oil.
By Paul from Caledon Canada on May 18, 2026.
Would recommend this to a friend.
Read all 187 reviews
Frequently asked questions
What dirt bikes is AMSOIL 10W-50 Synthetic Dirt Bike Oil for?
The 10W-50 grade is for dirt bikes whose service manual calls for SAE 10W-50 motorcycle oil, including four-stroke models from KTM, Husqvarna, Kawasaki, Yamaha, and Suzuki. Common applications include the KTM 450, 350, and 250 SX-F and EXC-F, Husqvarna FC and FE 450, 350, and 250, Kawasaki KX450 and KX250F, Yamaha YZ450F and YZ250F, and Suzuki RM-Z450 and RM-Z250 when the owner manual specifies a 10W-50 grade.
Is AMSOIL 10W-50 Synthetic Dirt Bike Oil JASO MA approved for wet clutches?
Yes. AMSOIL 10W-50 100% Synthetic Dirt Bike Oil meets JASO MA, the friction standard for shared-sump four-stroke motorcycle engines with wet clutches, and it carries API SG, SJ, SH, and SL service categories. Clutch-friction performance has been validated in an extreme simulated-start test against a leading OEM-branded oil.
10W-40 or 10W-50 dirt bike oil, which one is correct?
Pick the grade the dirt bike service manual specifies. KTM and Husqvarna 450, 350, and 250 four-strokes commonly call for SAE 10W-50, while many Honda CRF, Yamaha YZ-F, and Kawasaki KX-F models call for SAE 10W-40. The AMSOIL Synthetic Dirt Bike Oil family includes 10W-40, 10W-50, and 10W-60 grades. Substituting a 10W-40 in an engine that calls for 10W-50 is not recommended.
How often should AMSOIL 10W-50 Synthetic Dirt Bike Oil be changed?
Change AMSOIL 10W-50 Synthetic Dirt Bike Oil according to the dirt bike manufacturer's recommendations in the owner manual. KTM and Husqvarna competition four-strokes typically use short hour-based intervals on race fills, and hard-charging trail riders often shorten the interval further based on engine hours, fuel quality, and dust exposure.
Can passenger-car 10W-50 motor oil be used in a dirt bike?
Substituting passenger-car 10W-50 in a dirt bike that calls for a motorcycle oil is not recommended. Automotive oils often contain friction modifiers that can cause wet-clutch slippage and are not formulated for the shear loads of motorcycle transmission gears that share the engine sump.
Will AMSOIL Synthetic Dirt Bike Oil void a factory warranty?
No. AMSOIL 10W-50 Synthetic Dirt Bike Oil is Warranty Secure, keeping a factory warranty intact when used as a high-performance replacement for vehicle manufacturer-branded oils, and is backed by the AMSOIL Limited Warranty.
Can AMSOIL 10W-50 Synthetic Dirt Bike Oil be mixed with conventional oil?
AMSOIL 10W-50 Synthetic Dirt Bike Oil is compatible with other synthetic and conventional motor oils, so a mid-trip top-off will not cause damage. Mixing oils shortens the life expectancy of the AMSOIL formula and reduces its performance benefits, and extended drain intervals are not supported on mixed fills.
