[2019] "There are 12 tiers of oils that you can obtain"

https://www.pcinvasion.com/path-of-exile-blight-expansion-everything-you-need-to-know/2/

Edit: My math is probably wrong but there are 66 oil combinations for rings (tower buffs) and 220 combinations for amulets (notables including 13 secret passives)

Chris Mentioned the Secret Passives: https://www.pcinvasion.com/path-of-exile-blight-expansion-everything-you-need-to-know/2/

Seems like we should be able to catalog each arrangement fairly easily, though the ones using the highest tier will probably take a while or be held secret.

Just farm Glacier maps and 3->1 upgrade for the top oil once you get 177,147 of the lowest tier oil! EZ Game