Rustkill Undercoating is an oil based product sprayed on the the underside of your car to stop rust. Rustkill Undercoating locks out oxygen and stops rust dead in its tracks. Rustkill Undercoating is not rubberized undercoating, which can trap water, Ruskill Undercoating repels water. In addition, Rustkill Undercoating prevents new rust from forming because it stays where it is sprayed. As an added bonus, because Rustkill Undercoating is oil based, it gets rid of annoying chassis squeaks and helps to smooth your ride. We recommend applying Rustkill Undercoating one to two times per year. 1 quart is enough product to completely coat the underside of a typical car.