AMSOIL Gasoline Motor Oil
AMSOIL Signature Series is the top gasoline motor oil in the AMSOIL lineup, built for strong wear protection, clean operation, and dependable performance in demanding service.
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| Product code | Package size | Unit of measure |
|---|---|---|
| AMRQT-EA | Quart | Each |
| AMRQT-CA | Case of 12 Quarts | Case of 12 |
| AMR55-EA | 55 Gallon Drum | Each |
AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil is a heavy-grade, fully synthetic gasoline engine oil engineered for high-output and supercharged V8 engines that specify an SAE 5W-50 viscosity. The grade meets API SP, API SN Plus, Ford WSS-M2C931-C (Mustang), and GM dexos R, and supports extended drain intervals up to 25,000 miles in normal service.
Signature Series 5W-50 develops a robust fluid film that keeps metal surfaces separated, reinforced by anti-wear additives that reduce wear in metal-to-metal contact regions. The formulation provides 75 percent more engine protection against horsepower loss and wear than required by the industry standard, based on independent testing of Signature Series 0W-20 in the ASTM D6891 Sequence IVA Engine Test required by the API SN specification. The 5W-50 grade pairs that wear chemistry with a high-temperature high-shear viscosity of 4.45 cP at 150 C (ASTM D5481) for added bearing protection in supercharged builds.
Sustained high engine temperatures break weaker oils down and form deposits that rob horsepower. Signature Series 5W-50 uses an inherently stable synthetic base chemistry that resists oxidation and neutralizes acids over long periods. The Sequence IIIH Engine Test (ASTM D8111) required by ILSAC GF-6 and API SP runs at 304 F oil temperature to accelerate thickening, and the Signature Series formula limited oil thickening below the standard threshold even at doubled test length while delivering 40 percent cleaner pistons than the standard requires.
Forced-induction engines push oil through bearings that operate at extreme temperatures, where some oils form deposits in a process called turbo coking. Signature Series passed the GM Turbo Coking Test, a 2,000-cycle heat-soak protocol that requires an oil to limit the temperature change inside the turbocharger to 13 percent or less. The formula limited the increase to 3.6 percent, protecting the turbocharger 72 percent better than required by the GM dexos1 Gen 2 specification, based on independent testing of Signature Series 5W-30 in the GM turbo coking test.
Low-speed pre-ignition (LSPI) is the spontaneous ignition of the fuel and air mixture before the spark fires, and it is most damaging in turbocharged and supercharged gasoline direct-injection engines. Signature Series achieved 100 percent protection against LSPI, with zero events recorded in five consecutive runs of Signature Series 5W-30 in the LSPI engine test required for the GM dexos1 Gen 2 specification.
A heavy detergent treatment keeps oil passages and ring lands clean over long drain intervals, which matters more on engines that see hard runs followed by short cruise miles. Signature Series carries 50 percent more detergents than AMSOIL OE Motor Oil and delivers 28 percent more acid-neutralizing power than Mobil 1, based on testing of Mobil 1 Annual Protection Full Synthetic 5W-30 and Signature Series 5W-30 in ASTM D2896 with oils purchased July 2020. The formula also provides 90 percent better protection against sludge in the ASTM D6593 oil screen plugging engine test required by the API SN specification.
The 5W winter rating delivers usable cranking flow in cold conditions while the heavy 50-grade summer body holds shear-stable viscosity at temperature. Signature Series 5W-50 carries a CCS viscosity of 5108 cP at minus 30 C in ASTM D5293 Cold Crank Simulator testing required by SAE J300, a viscosity index of 185 (ASTM D2270), and a pour point of minus 48 C (minus 54 F) (ASTM D97). NOACK volatility is 6.1 percent in ASTM D5800 testing, which holds oil consumption down on engines that run hot under load.
Signature Series 5W-50 fits applications that require API SP, API SN Plus, or API SN, Ford WSS-M2C931-C (Mustang), or GM dexos R. The grade is intended for engines that specifically call for an SAE 5W-50 viscosity in the United States and Canada market, and the owner manual should list one of these service categories or OEM specifications before the oil is used.
AMSOIL Oil Filters are designed for extended drain intervals. With other-brand filters, the interval should not exceed 12,000 miles (19,312 km) or one year unless the vehicle manufacturer recommends a longer interval. Always change the filter when changing the oil, and check the level regularly. Signature Series 5W-50 is compatible with other conventional and synthetic motor oils, but mixing shortens oil life, reduces performance benefits, and is not supported for extended drain intervals. Aftermarket oil additives are not recommended for use with AMSOIL synthetic motor oils.
| Property | Value |
|---|---|
| Kinematic Viscosity at 100 C, cSt (ASTM D445) | 19.4 |
| Kinematic Viscosity at 40 C, cSt (ASTM D445) | 119.5 |
| Viscosity Index (ASTM D2270) | 185 |
| CCS Viscosity, cP at -30 C (ASTM D5293) | 5108 |
| Flash Point, C (F) (ASTM D92) | 224 (435) |
| Fire Point, C (F) (ASTM D92) | 244 (471) |
| Pour Point, C (F) (ASTM D97) | -48 (-54) |
| NOACK Volatility, percent weight loss (ASTM D5800) | 6.1 |
| High-Temperature High-Shear Viscosity at 150 C, cP (ASTM D5481) | 4.45 |
| Total Base Number (ASTM D2896) | 12.5 |
Signature Series 5W-50 is available as a quart bottle (product code AMRQT-EA), a case of 12 quarts (AMRQT-CA), and a 55 gallon drum (AMR55-EA). Using AMSOIL synthetic lubricants does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty. Match the right product with the AMSOIL vehicle lookup, compare grades and product positioning in the gasoline motor oil products, then order AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil.
I’ve been using AMSoil for so long I don’t remember when I started, but suffice to say I believe it’s the best oil on the market and when paired with the preferred customer membership it’s the the best value too.
Would recommend this to a friend.
The engine seems to run better
Would recommend this to a friend.
First time using this in my 2018 Silverado. So far it appears to be excellent. Quiet and smooth engine running. Will be using this oil exclusively from now on.
Would recommend this to a friend.
5W-50 is a heavy SAE J300 viscosity grade used in high-output gasoline V8s and supercharged performance engines that specify a 50-weight summer viscosity with cold-start flow of a 5W. Signature Series 5W-50 meets API SP, API SN Plus, Ford WSS-M2C931-C (Mustang), and GM dexos R.
Engines specifying Ford WSS-M2C931-C, including the Ford Mustang factory fill that uses this Ford performance specification, can run Signature Series 5W-50. Engines that require GM dexos R can also run this grade. Confirm the requirement against the owner manual or use the AMSOIL vehicle lookup.
Yes. Signature Series 5W-50 is a 100 percent synthetic gasoline engine oil. The base chemistry and long-drain additive system are inherently stable against oxidation and acid buildup over extended drain intervals.
Signature Series 5W-50 supports drain intervals up to 25,000 miles (40,200 km), 700 hours of operation, or one year, whichever comes first, for normal service in personal vehicles inside the United States and Canada. Severe service is capped at 15,000 miles (24,140 km), 700 hours, or one year. AMSOIL Oil Filters are recommended to take full advantage of the extended interval.
Substituting a 5W-30 in an engine that specifies 5W-50 is not recommended. The 50-weight summer viscosity protects bearing clearances designed around a heavier oil, particularly in supercharged or high-rpm builds. Use the AMSOIL vehicle lookup to confirm the correct viscosity for the vehicle.
The extended drain coverage applies to street-driven vehicles. Modified engines, racing vehicles, and engines running alternative fuels such as E85, CNG, or propane are excluded from extended drain recommendations. The oil can still be used in those applications on a shorter, application-specific change interval.
No. Using AMSOIL synthetic lubricants does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty.