* For most 4-cylinder engines (like the 2.5L): 10W-30 is usually recommended. However, check your manual; some might specify 5W-30, especially if it's a high-mileage engine.
* For the 4.0L 6-cylinder engine: 10W-30 is also typically recommended. Again, check your manual for the specific recommendation, as this might vary slightly depending on climate and driving conditions.
Crucially: The owner's manual will specify the oil type (conventional, synthetic blend, or full synthetic) and the correct API certification (e.g., API SN, SM, etc.). Using the wrong oil can severely damage your engine.
Before buying oil:
1. Locate your owner's manual: This is the most important step.
2. Check the engine: Look for an oil fill cap or dipstick – this usually indicates the engine size.
Don't rely solely on online information; always defer to your owner's manual for the precise oil requirements for your specific 1991 Jeep model and engine.
