* 2.5L Inline-4: This was a fairly common engine option.
* 2.8L V6: Also a popular choice.
* 4.3L V6: A more powerful V6 option.
To know for sure what engine *a specific* 1990 Chevy S-10 has, you'd need to check the vehicle's identification number (VIN) or look for the engine size stamped on the engine block itself.