However, generally speaking, for a 1999 Mustang, you'll likely need either:
* 5W-30: This is a common weight for many engines and is a good starting point if you don't have your owner's manual.
* 10W-30: Also common, particularly in warmer climates.
Crucially, the owner's manual will specify whether it needs conventional, synthetic blend, or fully synthetic oil. Using the incorrect type of oil can damage your engine.
If you can't find your owner's manual, you can try searching online for a PDF version using your VIN number (Vehicle Identification Number). This number is usually found on the driver's side dashboard. You can also consult a trusted mechanic or auto parts store, providing them with your Mustang's engine size.
