However, as a general guideline, many 2005 Chevy Tahoes used 5W-30 oil. This is a common viscosity for many vehicles, but again, check your owner's manual for the specific recommendation for YOUR Tahoe's engine. Using the incorrect oil can damage your engine.
Look for the information on the oil fill cap, or a sticker under the hood, as well. These might give clues to the correct oil type.