What type of engine oil should be put into a 2003 GMC Sonoma?

The type of engine oil for your 2003 GMC Sonoma depends on the engine it has. Sonoma's from that year could have several different engines. You MUST check your owner's manual to determine the correct oil type and viscosity.

The manual will specify the:

* Oil type: This will likely be a conventional, synthetic blend, or full synthetic oil. It might also specify if it needs to meet a specific API (American Petroleum Institute) certification, such as SM, SN, or SP (newer standards supersede older ones).

* Oil viscosity: This is usually expressed as something like 5W-30, 10W-30, or 5W-40. The viscosity is crucial for proper lubrication at different temperatures. Using the wrong viscosity can damage your engine.

Without knowing the engine in your specific 2003 GMC Sonoma, I cannot give you the correct oil type. Checking your owner's manual is the only reliable way to determine the correct oil specifications.