Collecting Used Oil for Recycling/Reuse For years, motor oil commonly was reused or discarded in ways that neither protected the environment nor conserved its resource value. In the United States alone, an estimated 200 million gallons of used motor oil are improperly disposed of by being dumped on the ground, tossed in the trash (ending up in landfills), and poured down storm sewers and drains. Just one gallon of used oil has the potential to contaminate up to one million gallons of drinking water. Additionally, used oil that ends up in the country's rivers, lakes, and streams can threaten aquatic life.