General Recommendation:
For a 1990 Jeep Cherokee with a high-mileage engine, a high-quality 10W-30 or 10W-40 conventional or synthetic blend motor oil is a good starting point. The 10W part indicates good cold-weather performance, while the 30 or 40 indicates the viscosity at operating temperature. The higher number (40) is thicker and better for higher mileage engines that might have more wear, but in warmer climates, 30 might be preferable.
Factors to Consider:
* Engine type: Does your Cherokee have a 4.0L inline-six or a different engine? The owner's manual will specify the recommended viscosity. The 4.0L is the most common, but it's crucial to confirm.
* Climate: Colder climates benefit from a lower second number (like 30), while hotter climates might prefer a higher number (like 40).
* Driving conditions: Severe driving conditions (lots of stop-and-go traffic, towing) may benefit from a slightly thicker oil.
* Oil type: Conventional oil is the most affordable, synthetic blend offers a balance of price and performance, and full synthetic is the most expensive but offers the best protection and longevity. For a high mileage engine, a synthetic blend is often a good compromise.
* Owner's manual: The most definitive answer is in your owner's manual. It will specify the recommended viscosity and API certification (like SJ, SL, SM, etc.). Older specs are fine for older vehicles; newer ones are backward compatible.
Finding the Right Oil:
1. Check your owner's manual: This is the primary source for the manufacturer's recommendation.
2. Look for API certifications: The American Petroleum Institute (API) certifies motor oils. Look for a certification that meets or exceeds the recommendation in your owner's manual.
3. Consider your budget and climate: Balance the cost of the oil with your needs based on the climate and driving conditions.
In short: Start with a 10W-30 or 10W-40 conventional or synthetic blend motor oil that meets or exceeds the API certification specified in your owner's manual. Always double-check your owner's manual for the most accurate information.
