AMSOIL 15W-50 100% Synthetic Small-Engine Oil Delivers commercial-grade protection and outperforms conventional oils. Tough formulation protects against wear, heat, and carbon deposits. Helps maintain power and promotes long engine life. Specifically designed for maximum equipment dependability. Service life up to 200 hours.
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Product data sheets
View, download, or save a copy of the Product Data Sheet or Safety Data Sheet for AMSOIL 15W-50 100% Synthetic Small Engine Oil.
AMSOIL 15W-50 100% Synthetic Small Engine Oil is the heaviest grade in the commercial-grade synthetic small-engine family, formulated for 4-stroke outdoor power equipment that calls for an SAE 50, 10W-50, or 15W-50 motor oil. The 15W-50 is built for hot-climate continuous-duty service: commercial mowing, generators running through summer heat, log splitters under sustained load, and industrial pressure-washer use.
Shear-stable wear protection
Small engines run under near-constant load, and high-output V-twins exert heavy shear on the oil film at every cycle. The 15W-50 is a shear-stable, high-film-strength formulation fortified with anti-wear additives that does not thin out under mechanical shear, ensuring a continuous lubricating film that protects against metal-to-metal contact. Four-Ball Wear Testing per ASTM D4172B returns a 0.42 mm wear scar for the 15W-50 grade, the lowest in the small-engine family, indicating strong boundary protection in the bearing and ring zones that take the heaviest load in high-output equipment.
High-temperature film strength
The 15W-50 is engineered for hot operating temperatures and heavy continuous loads where a 10W-30 or 10W-40 would thin past its safe operating range. Kinematic viscosity at 100 C is 17.8 cSt per ASTM D445, the thickest grade in the small-engine family, supporting a robust hot-film cushion in the bearing, cam, and ring zones. High-Temperature High-Shear viscosity at 150 C measures 4.9 cP per ASTM D4683, well above the 3.5 cP minimum required of an SAE 40-grade and above, providing the durable hydrodynamic film called for in commercial cutting and prolonged full-load duty.
Heat-resistant base oils and low oil consumption
Air-cooled small engines run hotter than liquid-cooled automotive engines and burn more oil when the base oil flashes off. The 15W-50 uses heat-resistant synthetic base oils with very low volatility, posting NOACK Volatility of 3.2 percent weight loss in ASTM D5800 testing, the lowest in the small-engine family. In 125-hour lab tests of AMSOIL 10W-30 Synthetic Small-Engine Oil against three leading 10W-30 and SAE 30 motor oils, the synthetic small-engine formulation reduced oil consumption 61 percent, a family-wide benefit driven by the same heat-resistant chemistry used in the 15W-50.
Power preservation and deposit control
Engine power is reduced by wear, carbon deposits, and stuck rings and valves. The 15W-50 prevents ring and valve sticking and helps eliminate carbon deposit formation so engines produce maximum power across their service lives. After 500 hours of severe-service testing in a Kawasaki FX 730V engine, the piston and rings remain virtually free of deposits and wear. Saturated synthetic base oils and potent antioxidants resist extreme heat, while detergents fight carbon, varnish, and sludge. A Total Base Number of 11.6 gives the 15W-50 strong reserve alkalinity to neutralize acids over a full 200-hour service interval.
Commercial-grade formulation
Many small-engine oils on the market are relabeled automotive oils tuned for fuel economy. The 15W-50 is engineered for the demands of small engines in continuous-duty service, with a fortified additive package that targets wear, power loss, oil consumption, carbon deposits, and stuck rings and valves. The oil contains no friction modifiers and meets JASO MA and MA2 wet-clutch standards, helping prevent misapplication when the same bottle is used across mowers, generators, and certain transmissions.
Recommended applications and service intervals
AMSOIL 15W-50 100% Synthetic Small Engine Oil is built for gasoline 4-stroke engines and certain off-road diesel engines that require any of the following service categories: API SL, SJ, SH, SG (gasoline), API CD, CF (diesel), and JASO MA or MA2 (wet clutch). It is intended for zero-turn, riding, stand-on, and push mowers, generators, power washers, and other similar equipment that requires SAE 50, 10W-50, or 15W-50 motor oil.
Service life: up to 200 hours or one year, whichever comes first, in severe-service small-engine duty, based on extensive severe-service testing.
Use only in equipment that specifies SAE 50, 10W-50, or 15W-50. For SAE 30, 5W-30, 10W-30, 10W-40, or 15W-40 applications, choose the matching small-engine grade.
Aftermarket oil additives are not recommended for use with AMSOIL Synthetic Small-Engine Oil.
Outside the United States and Canada, follow the equipment manufacturer's recommended drain interval.
The 15W-50 is compatible with other synthetic and conventional motor oils, but mixing shortens oil life and reduces performance benefits, and extended drain intervals are not supported when oils have been mixed. Pair the oil with a fresh small-engine oil filter at every change to take full advantage of the extended interval.
Typical technical properties
Property
Value
Kinematic Viscosity at 100 C, cSt (ASTM D445)
17.8
Kinematic Viscosity at 40 C, cSt (ASTM D445)
128.9
Viscosity Index (ASTM D2270)
153
CCS Viscosity, cP at -20 C (ASTM D5293)
5128
Pour Point, C (F) (ASTM D97)
-36 (-33)
Flash Point, C (F) (ASTM D92)
234 (453)
Fire Point, C (F) (ASTM D92)
262 (504)
Four-Ball Wear Test, scar, mm (ASTM D4172B at 40 kg, 75 C, 1,200 rpm, 1 hr)
0.42
NOACK Volatility, percent weight loss (ASTM D5800)
3.2
High-Temperature High-Shear Viscosity at 150 C, cP (ASTM D4683)
4.9
Total Base Number
11.6
Order AMSOIL 15W-50 100% Synthetic Small Engine Oil
The 15W-50 is available in quart (SEFQT-EA) and case of 12 quarts (SEFQT-CA). All AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty, and the formulation is Warranty Secure, keeping the equipment manufacturer warranty intact when used in place of branded service oil. Match the right grade to the equipment with the AMSOIL Vehicle Lookup Guide, compare viscosities and applications in the Small Engine Oil Guide, then order AMSOIL 15W-50 100% Synthetic Small Engine Oil.
SAE 15W-50 small-engine oil is a heavy-grade 4-stroke synthetic oil for outdoor power equipment that runs in high ambient temperatures, continuous-duty cycles, or under heavy sustained load. AMSOIL 15W-50 100% Synthetic Small Engine Oil is intended for zero-turn, riding, stand-on, and push mowers, generators, power washers, and similar equipment that specifies SAE 50, 10W-50, or 15W-50 motor oil. The grade is a strong fit for commercial mowing in hot climates, generators running through summer, and industrial pressure-washer service.
Can 15W-50 be used in a lawn mower or commercial mower?
The 15W-50 is intended for mowers and other 4-stroke outdoor power equipment that specify SAE 50, 10W-50, or 15W-50. Heavy-output commercial V-twins from manufacturers like Vanguard, Kohler, Kawasaki, and Briggs and Stratton may call for or allow a 15W-50 in hot-weather service. For an engine that calls for SAE 30, 5W-30, 10W-30, 10W-40, or 15W-40, use the matching small-engine grade. Verify the correct viscosity for the specific mower with the AMSOIL Vehicle Lookup Guide.
Why pick 15W-50 over a 10W-30 or 10W-40 small-engine oil?
The 15W-50 grade carries a thicker hot-temperature film than lighter small-engine grades. Kinematic viscosity at 100 C is 17.8 cSt and High-Temperature High-Shear viscosity at 150 C is 4.9 cP, both higher than the 10W-30 or 10W-40 grades in the same family. That thicker hot film protects bearings, cams, and rings in equipment that runs at sustained full load or in hot ambient conditions, where a lighter oil can thin past its safe operating range.
Is synthetic oil good for small engines?
Yes. Synthetic base oils have a higher viscosity index, lower volatility, and better thermal stability than conventional oils, which directly addresses the heat, full-load duty, and oil burn-off that wear small engines down. The 15W-50 grade combines those base oils with anti-wear additives, antioxidants, and detergents engineered for air-cooled 4-stroke service, and posts a NOACK Volatility of 3.2 percent in ASTM D5800 testing.
How long can the 15W-50 stay in service?
AMSOIL 15W-50 100% Synthetic Small Engine Oil supports a service life of up to 200 hours or one year, whichever comes first, based on extensive severe-service testing of the synthetic small-engine family. It provides an extra measure of protection when equipment goes longer between oil changes than the equipment manufacturer recommendation.
Will using AMSOIL synthetic oil void a small-engine warranty?
No. Using AMSOIL synthetic lubricants does not void a new equipment manufacturer warranty. The 15W-50 is Warranty Secure and is covered by the AMSOIL Limited Warranty when used as a replacement for branded service oil.
Can the 15W-50 be mixed with conventional small-engine oil?
The 15W-50 is compatible with other synthetic and conventional motor oils, but mixing shortens oil life and reduces performance benefits. Extended drain intervals are not supported when oils have been mixed, and aftermarket oil additives are not recommended for use with AMSOIL Synthetic Small-Engine Oil.
