The recommended oil for a 1999 Chevy Lumina depends on the engine it has. The Lumina came with several engine options. To know for sure,
you need to check your owner's manual. It will specify the correct oil type (conventional, synthetic blend, or full synthetic) and viscosity (like 5W-30 or 10W-30).
However, common recommendations for many 1999 Lumina engines were 5W-30 or 10W-30. Again, consult your owner's manual for the exact specifications for *your* Lumina's engine. Using the wrong oil can damage your engine.
