HHO generators -- hydrogen generators to many -- work by a method called electrolysis. Water is split into individual components hydrogen (H2) and oxygen (O). These gases mix with the fuel in the engine and ignite, creating a higher octane fuel. The higher octane, in return, contributes to more complete fuel burning, reduced emissions, smoother running and the end result -- more miles per gallon for your car.
The electrolysis process relies on the application of an electrical current inside the HHO cell. The cell contains distilled water and an electrolyte -- preferably sodium hydroxide (NaOH). While some use baking soda or potassium hydroxide (KOH), sodium hydroxide -- better known as lye -- is considered superior in performance to baking soda and more readily available than potassium hydroxide.
Calculating the Amount
Most cars operate efficiently when they produce 4 to 20 amps of electrolysis. This equates into, at most, 1/4 ounce (about 2 teaspoons) per quart of water, or 1 ounce (8 teaspoons) per gallon. Test the solution with a DC amp meter to test the amp draw: too high and the HHO cell will run hot.