* Automatic Transmission: Most likely, it uses Dexron-III. However, check your owner's manual. It's *crucial* to use the correct fluid specified by GM for your specific transmission. Using the wrong fluid can severely damage the transmission. Even within Dexron-III, there might be specific GM specifications.
* Manual Transmission: Manual transmissions in the S10 generally used GL-4 or GL-5 gear oil. Again, consult your owner's manual for the exact specification. The viscosity (like 75W-90 or 80W-90) will also be specified.
Do not rely on general advice. Look up the information in your owner's manual. If you don't have the manual, you can often find a PDF version online by searching for "[Your S10's VIN] owner's manual" or visiting the Chevrolet website. If you're still unsure, contact a Chevrolet dealership or a reputable auto parts store; they can help you identify the correct fluid based on your truck's VIN.
