BuildCraft version: buildcraft_1.12.2_7.99.14
Forge version: Forge 14.23.4.2705
Link to crash report or log: screenshot -> https://imgur.com/a/8vbEmg8
Singleplayer or multiplayer: Singleplayer
Steps to reproduce: Generation
Additional information: Please fix oil-generation class file.

not sure what's wrong here?
also your BC version is outdated, latest version for 1.12.2 is 7.99.17