However, as a general guideline:
* Consult your owner's manual: This is crucial. The recommended oil will be based on your engine's specific needs and operating conditions.
* Look for the recommended viscosity: This is usually a number like 5W-30 or 10W-30. The lower the first number, the better the oil flows in cold temperatures. The higher the second number, the better the oil's protection at high temperatures.
* Consider the oil type: Conventional oil is the cheapest, followed by synthetic blends, and then full synthetic. Full synthetic generally offers better performance and longevity. Your owner's manual will likely indicate whether or not synthetic oil is acceptable. Many Wranglers do perfectly well with synthetic blends, offering a good balance of price and performance.
* API Certification: Make sure the oil you choose meets the API (American Petroleum Institute) certification requirements specified in your owner's manual.
Without knowing your specific engine, I cannot give you a precise recommendation. Always defer to your owner's manual. You can also find this information on the oil cap or a sticker located in the engine bay.