What type oil to put in a 1998 buick regal supercharged?

The 1998 Buick Regal Supercharged used a 3.8L supercharged V6 engine. The recommended oil type depends on the operating temperature in your area and your driving habits. However, consult your owner's manual for the most precise and up-to-date recommendation. The manual will specify the viscosity (like 5W-30 or 10W-30) and the API (American Petroleum Institute) certification (like SM or SN – newer certifications are usually better).

Generally, for a 1998 vehicle, a conventional 5W-30 or 10W-30 oil meeting the API recommendations in your owner's manual would be suitable. You could also use a synthetic blend or full synthetic oil of the same viscosity if you prefer. Using a higher viscosity oil than recommended could hurt performance and fuel economy; a lower viscosity than recommended may lead to insufficient lubrication.

Never ignore the information in your owner's manual. This is the definitive source for your specific vehicle's needs.