Generally speaking, for a 1998 3.8L Mustang, a 5W-30 or 10W-30 oil meeting the API requirements specified in your owner's manual is a safe bet. 5W-30 is often preferred for its better cold-weather performance. 10W-30 might be slightly better for warmer climates or higher mileage engines.
Beyond the basics, consider these factors:
* Mileage: Higher mileage engines might benefit from a high-mileage specific oil, often containing additives to help with seal conditioning.
* Driving conditions: If you frequently drive in extreme temperatures (very hot or very cold), choose an oil appropriate for those conditions.
* Synthetic vs. Conventional: Synthetic oils generally offer better performance and longevity, but are more expensive. Conventional oils are a more budget-friendly option. Many people successfully use conventional oil in these engines, especially if the car is primarily used for shorter trips.
Before making a choice, always check your owner's manual for the manufacturer's specific recommendations. This is the most reliable source of information for your vehicle. Ignoring these recommendations could void your warranty (if applicable) and potentially damage your engine.
