A quart bottle of AMSOIL 5W-50 Signature Series Synthetic Oil for Ford Mustangs.This 5W-50 Synthetic Oil for high-output Ford Mustang engines covers the Ford WSS-M2C931-C and WSS-M2C931-B specifications for supercharged 5.8 liter, 5.4 liter, 5.2L Voodoo and Boss 302 (5.0L) engines. We can sell this 100% synthetic 5W-50 Mustang engine oil at wholesale prices in Canada and the USA. Please contact us for a price list using the form on this page or call us at 1-800-748-5781. Read more about the new formula.

AMSOIL Synthetic 5W-50 package sizes include:
-Single US Quart Bottle
-Case of 12 US Quarts

Signature Series stacks up against any motor oil out there. I have no hesitation in calling it the world’s best.  – AMSOIL Chief Operating Officer Alan Amatuzio on the latest Signature Series reformulation. October, 2017

Suitable Applications For AMSOIL 5W-50 Signature Series Synthetic Oil For Mustangs

This 100% synthetic oil is suitable for supercharged and naturally aspirated Mustang engines requiring the following specifications:

  • Ford WSS-M2C931-C and WSS-M2C931-B
  • API SN, SM

Applicable high-output Mustang engines include:

  • 5.8L (engine code: Z)
  • 5.4L (engine code: S)
  • 5.2L (engine code: 99Z)
  • 5.0L (engine code U)

AMSOIL 5W-50 Signature Series Synthetic Oil is an elite replacement for the following:

  • Quaker State Ultimate Durability Full Synthetic Oil SAE 5W-50
  • Motorcraft SAE 5W-50 Full Synthetic Motor Oil
  • Red Line High Performance Synthetic 5W-50 Motor Oil

Features and Benefits of AMSOIL 5W-50 Signature Series Synthetic Oil

  • AMSOIL synthetic wear control
  • Combats shearing
  • Prevents internal deposits
  • Withstands extreme heat
  • Strong resistance to oil consumption
  • Excellent for superchargers
  • Capable of long service intervals
Ford Mustang Shelby GT500

AMSOIL 5W-50 Signature Series Synthetic Engine Oil is designed for Shelby GT500 and Boss 302 Ford Mustangs. (photo credit: onallcylinders.com)

The Ultimate Wear Protection For Mustang Engines

AMSOIL couples a robust 100% synthetic base oil with the finest anti-wear additive package in the industry to give your high-output Mustang the best possible wear control. AMSOIL 5W-50 provides a relentless film strength that cushions internal engine components from severe shock loads, extreme heat and high RPM.

Designed To Withstand Extreme Heat

This powerful synthetic formula withstands extreme heat in Shelby GT500, GT350 and Boss 302 engines. AMSOIL 5W-50 maintains its viscosity during hot operating conditions without thickening or shearing down. It resists deposits, so engine internals remain free of sludge and varnish. The high resistance to volatility keeps oil consumption at bay.

Mixing AMSOIL Synthetic 5W-50 with Other Brands

AMSOIL 5W-50 Signature Series Synthetic Oil is compatible with all other brands of conventional, synthetic-blend and full-synthetic motor oils. While you can safely mix AMSOIL Synthetic Oil with other brands, this will reduce the drain interval and performance capabilities of AMSOIL 5W-50.

Service Life of AMSOIL 5W-50 Signature Series Synthetic Oil

AMSOIL 5W-50 Signature Series Synthetic Oil is overbuilt for long service interval capability.

For Supercharged or modified* engines:

  • Up to 15,000 miles (24,000 km), 700 hours of running time or one year, whichever comes first.

For naturally aspirated engines (that are unmodified*):

  • Up to 25,000 miles (40,000 km), 700 hours of running time or one year, whichever comes first.

* Engines operating under modified conditions (non-stock) are excluded from extended drain recommendations. Examples include the use of performance computer chips; non-OEM approved exhaust, fuel or air induction systems; and the use of fuels other than those recommended for normal operation by the manufacturer.


Signature Series 100% Synthetic 5W-50 Motor Oil

Viscosity @ 100°C, cSt (ASTM D-445)


Viscosity @ 40°C, cSt (ASTM D-445)


Viscosity Index (ASTM D-2270)


VISC. CCS, cP (ASTM D-5293)

5108 (-30)

Flash Point °C (°F) (COC) (ASTM D-92)

224 (435)

Fire Point °C (°F) (COC) (ASTM D-92)

244 (471)

Pour Point °C (°F) (ASTM D-97)

-48 (-51)

NOACK (% weight loss) (ASTM D-5800)


High Temperature/High Shear Viscosity
@ 150°C, 1.0 X 106 s.-1), cP (ASTM D-5841)


Total Base Number (ASTM D-2896)