It’s important to remember that “oil” isn’t actually one homogenous product. It comes in lots of different densities, forms and sulfuricities (ed: is that even a word?), and therefore has a myriad different usages, buyers and prices, in different parts of the world.
https://archive.ph/IGSnL#selection-1983.0-1987.100

https://archive.ph/Gi4Wq
The pullback is sharpest in jet fuel (down more than 40%), followed by gasoline (down more than 30%) and diesel (down more than 20%).