* API Certification: Look for an oil with an API certification that meets or exceeds the requirements specified in your owner's manual. This is crucial for engine protection. Older manuals might specify SG, SH, SJ, or SL. Modern oils often exceed these specifications.
* Viscosity: The owner's manual will recommend a viscosity grade, typically expressed as something like 10W-30 or 5W-30. This describes the oil's thickness at different temperatures. Choosing the correct viscosity is vital for proper lubrication and engine performance. Using the wrong viscosity can lead to reduced fuel economy or even engine damage. Check your owner's manual carefully as this is the most important specification. If you can't find the manual, a search online for "1997 Jeep Wrangler 4-cylinder owner's manual" should help.
* High-Quality Brand: While many brands offer suitable oil, sticking to reputable brands like Mobil 1, Castrol, Valvoline, Pennzoil, or Quaker State generally ensures consistent quality and performance.
In summary: Consult your owner's manual FIRST. It will specify the recommended oil viscosity and API certification. Then, choose a high-quality oil that meets or exceeds those specifications. If you can't find the manual, using a 10W-30 or 5W-30 oil that meets at least an API SJ specification is a reasonable starting point, but always prioritize information from the owner's manual.
