Lucky blight chests

Several oils grant x chests are lucky...But what is the difference. i have used and not used this mod and cant tell the difference or which chests are even lucky. Searched around and cant find info on this.

Look at https://pathofexile.gamepedia.com/Luck which explains the "lucky" perc one.

The gamepedia page you linked only discusses luck with respect to damage and so it not abundantly clear how it applies to chests.

However the fundamental element is that when the chests spawn, you get a 2nd chance of what it spawns.

Typically when the initial spawn is occurring the first 'check' is if it is valuable or not. I can only assume that when it is a lucky chest, if the first check states it is not valuable, then the lucky element kicks in and rolls again, so the 2nd first check occurs. Ultimately gives you a 2nd chance to have good chests.