• The 2005 Ford Mustang is equipped with a 4-liter, six-cylinder engine as standard equipment. The 4-liter engine relies, in part, on oil to cool the engine. However, the primary purpose of the oil is to lubricate the engine's internal moving components. The ability of oil to accomplish either task diminishes over time. For this reason, the oil should be replaced with the correct type of oil and at the appropriate intervals.
  
  

Oil Change Interval

• Ford recommends an oil change every 5,000 miles if the car is used under normal driving conditions. If the Mustang if often driven at a low speed, is left idling for extensive periods of time, or is driven regularly in dusty conditions, Ford recommends an oil change every 3,000 miles.
  
  

Viscosity

• Viscosity refers to the thickness of the oil. Ford recommends using oil with a viscosity rating of 5W-30 for the 4-liter.
  
  

API Certified Oil

• Ford recommends only using a type of oil "certified for gasoline engines" by the American Petroleum Institute (API). Certified oil contains a circular stamp prominently displayed on the oil container.