Collecting and processing more than 200 million gallons of oil per year, Safety-Kleen is the largest re-refiner of used oil in North America. Our closed-loop system begins with oil collection from thousands of locations across the country. Once collected, it is sent to one of our re-refineries for processing, where all of the contaminants and impurities are removed, leaving the oil as clean and pure as the day it was first refined.