Bleach is one of the worst things a person can put in a gas tank, according to Reference. This is because it can react with gas chemicals and cause acid to form in the tank. The acid then causes the tank to rust prematurely, as well as the fuel lines, and can cause the engine to stall.
If bleach is added to a car's gas tank, it should be flushed out with water immediately. The car's owner should also flush out the fuel lines and replace the car's fuel filter.
According to Reference.com, adding bleach to a gas tank is not advisable, but it is not likely to cause any long-term problems with the vehicle. The source reminds that the only thing that belongs in a gas tank besides gas is a gas treatment, which can be added to the car's gas tank. The purpose of the gas treatment is to flush out water that may have been added accidentally or may have been in the purchased gas.
According to Reference.com, many believe that sugar is the worst thing for a fuel tank. Sugar clogs a fuel filter and causes the car to stop running. The car's gas tank must be removed so that the sugar can be dumped out.