If I load _any_ previous save of my game before today the pipeline that should have light oil is blocked by petroleum. In some instances the machines using the light oil are still active with light oil in their buffers, meaning the pipeline was seemingly fine moments before the save was made. This is across saves that are hours apart, so if petroleum had erroneously entered the system in the previous save then the machines using the pipeline wouldn't still be active hours later.
I had previously encountered this twice before, first time I thought it was my mistake and fixed it, the 2nd time I assumed I accidentally continued from a save before I had fixed it, and now.