The main active ingredient in our octane boosters is air and light sensitive. If the bottle has remained sealed this whole time, it may very well still be good. If it’s been opened, it might be bad. The easiest way to tell is to take a flashlight and look inside the bottle. If it’s clear all the way to the bottom, then it’s ok. If it has some black precipitate, it has started to go bad and should not be used.