AMSOIL SIGNATURE SERIES 5W-50 100% SYNTHETIC MOTOR OIL

AMSOIL Signature Series 5W-50 100% Synthetic Motor Oil delivers maximum wear protection and thermal stability for high-output engines that run hard, run hot, and need an oil that won't quit. Built for performance-oriented vehicles and modified engines where a heavier viscosity grade is required, this is the oil professional engine builders trust when failure is not an option.

High-performance and modified engines generate tremendous heat and mechanical stress that push conventional oils and even many synthetics past their limits. Engines calling for 5W-50 viscosity are typically working harder than average, whether they're turning laps on a road course, running a supercharged Ford Mustang GT500 at wide-open throttle, or simply built with looser tolerances that demand a thicker oil film. In these conditions, thermal breakdown, deposit formation, and accelerated cam and bearing wear are real threats that the wrong oil cannot manage.

75% MORE PROTECTION AGAINST HORSEPOWER LOSS AND WEAR
The Sequence IVA Engine Test (ASTM D6891) simulates extended stop-and-go driving for 100 hours, cycling between idle and elevated rpm to punish the oil film and accelerate cam lobe wear. The camshaft is then measured in 84 locations. AMSOIL Signature Series delivered an average cam wear score of just 20.28 microns, compared to the 90-micron industry standard limit. That is 75% more protection than the API SN PLUS specification requires. This level of wear resistance directly preserves cam profiles, piston rings, and bearing surfaces over tens of thousands of miles. In a 100,000-mile independent test using Ford F-150 trucks with 3.5L twin-turbo EcoBoost engines, Signature Series maintained horsepower and torque from start to finish, keeping bearings looking like new.

GUARDS TURBOCHARGERS AGAINST COKING
The extreme heat generated by turbochargers can cause lesser oils to oxidize and form carbon deposits on the turbo bearing and shaft surfaces. This process, known as turbo coking, gradually restricts oil flow and can lead to premature turbo failure. The GM Turbo Coking Test subjects the oil to 2,000 extreme heat-soak cycles. To pass, the oil must limit the temperature change within the turbocharger to 13% or less. Signature Series limited the increase to just 3.6%, protecting the turbocharger 72% better than required by the GM dexos1 Gen 2 specification. For turbocharged engines like the Ford 5.0L Coyote with aftermarket forced induction or the Mustang Shelby GT500's supercharged 5.2L, this thermal resilience is critical.

RESISTS VISCOSITY BREAKDOWN UNDER EXTREME HEAT
Signature Series was tested in the Sequence IIIH Engine Test (ASTM D8111) at oil temperatures of 304°F (151°C), well above normal operating range. After the standard 90-hour test, viscosity had increased only 0.1% against a 100% allowable threshold. The lab then reassembled the engine and ran the test again using the same oil. Even after doubling the test length, Signature Series limited viscosity increase to 49.6%, still well under the standard, and delivered 40% cleaner pistons than the specification requires. The 5W-50 viscosity grade starts with a kinematic viscosity of 19.4 cSt at 100°C and a high-temperature/high-shear viscosity of 4.45 cP at 150°C, providing a robust, stable oil film that holds up under sustained high-rpm operation and elevated temperatures.

MAXIMUM CLEANING POWER AND SLUDGE RESISTANCE
Signature Series carries 50% more detergent additives than AMSOIL OE Motor Oil and delivers 28% more acid-neutralizing power than Mobil 1 Annual Protection 5W-30 as measured in ASTM D2896 testing. A Total Base Number of 12.5 gives this oil significant reserve alkalinity to neutralize combustion acids over long drain intervals. In the Sequence VG Engine Test (ASTM D6593), which subjects a Ford 4.6L engine to 216 hours of sludge-inducing conditions, Signature Series produced an oil pick-up tube screen virtually free of sludge, providing 90% better protection against sludge than the API SN specification allows.

100% PROTECTION AGAINST LOW-SPEED PRE-IGNITION
LSPI is the spontaneous ignition of the fuel-air mixture before spark-triggered ignition in modern gasoline direct injection engines. It can shatter piston ring lands and destroy engines in seconds. Signature Series achieved zero LSPI events across five consecutive tests as required by the GM dexos1 Gen 2 specification. For forced-induction applications where cylinder pressures run high, this is a formulation-level safeguard that matters at every cold start and part-throttle transient.

SPECIFICATIONS AND COMPATIBILITY
AMSOIL Signature Series 5W-50 (AMR) meets API SP, SN PLUS, SN and earlier. It also carries Ford WSS-M2C931-C approval, which is the factory specification for the Ford Mustang GT and Shelby models calling for 5W-50. It meets GM dexos R for performance applications. This oil is compatible with other conventional and synthetic motor oils, though mixing will reduce the performance benefits and shorten drain interval capability. Aftermarket oil additives are not recommended.

SERVICE LIFE
Normal service: up to 25,000 miles, 700 hours of operation, or one year, whichever comes first. Severe service (commercial or fleet vehicles, excessive idling, frequent towing, hauling, plowing, or dusty conditions): up to 15,000 miles, 700 hours, or one year. Modified (non-stock) engines, racing vehicles, and vehicles using alternative fuels (E85, CNG, propane) are excluded from extended drain interval recommendations. When using non-AMSOIL oil filters, do not exceed 12,000 miles or one year. Always change the filter when changing oil.