There are microbes that break down hydrocarbons for energy, but they aren't necessary for oil to break down. Hydrocarbons can break down on their own, which is

There are microbes that break down hydrocarbons for energy, but they aren't necessary for oil to break down. Hydrocarbons can break down on their own, which is why you are supposed to change your cars oil every 3 months regardless of how many miles you drive.