The type of oil a 1999 Chevy Blazer needs depends on the engine it has. There were several engine options available that year. To know for sure,
you need to check your owner's manual. It will specify the recommended oil type (e.g., 5W-30, 10W-30) and the API certification (like SM, SL, etc.).
Without knowing the specific engine, I can only give general advice: Most likely, a 1999 Chevy Blazer would use a conventional or synthetic blend 5W-30 or 10W-30 motor oil. However, always defer to the information in your owner's manual. Using the incorrect oil can damage your engine.
