testing versions A4.0.0 - A1.6.2.4.1.0
Please help

Did you do something with the configuration files for BuildCraft?

If you copied an "old" world (pre 4.1.0) into a new Minecraft Launcher profile with updated mods, then you must remember to also copy the configuration files.

1521 used to be the block id for Oil, I'm not sure what happened to existing worlds when BC moved to the forge fluids