Automotive oil recycling
Automotive oil recycling involves the recycling of used oils and the creation of new products from the recycled oils, and includes the recycling of motor oil and hydraulic oil. Oil recycling also benefits the environment: increased opportunities for consumers to recycle oil lessens the likelihood of used oil being dumped on lands and in waterways. For example, one gallon of motor oil dumped into waterways has the potential to pollute one million gallons of water.
Recycled motor oil can be combusted as fuel, usually in plant boilers, space heaters, or industrial heating applications such as blast furnaces and cement kilns. Recycled motor oil can be distilled into diesel fuel or marine fuel in a process similar to oil re-refining, but without the final hydrotreating process. The lubrication properties of motor oil persist, even in used oil, and it can be recycled indefinitely. 
Used motor oil re-refining
Used oil re-refining is the process of restoring used oil to new oil by removing chemical impurities, heavy metals and dirt. Used Industrial and automotive oil is recycled at re-refineries. The used oil is first tested to determine suitability for re-refining, after which it is dehydrated and the water distillate is treated before being released into the environment. Dehydrating also removes the residual light fuel that can be used to power the refinery, and additionally captures ethylene glycol for re-use in recycled antifreeze.
Next, industrial fuel is separated out of the used oil then vacuum distillation removes the lube cut (that is, the fraction suitable for reuse as lubricating oil) leaving a heavy oil that contains the used oil's additives and other by-products such as asphalt extender. The lube cut next undergoes hydro treating, or catalytic hydrogenation to remove residual polymers and other chemical compounds, and saturate carbon chains with hydrogen for greater stability.
Final oil separation, or fractionating, separates the oil into three different oil grades: Light viscosity lubricants suitable for general lubricant applications, low viscosity lubricants for automotive and industrial applications, and high viscosity lubricants for heavy-duty applications. The oil that is produced in this step is referred to as re-refined base oil (RRBL).
The final step is blending additives into these three grades of oil products to produce final products with the right detergent and anti-friction qualities. Then each product is tested again for quality and purity before being released for sale to the public.
- Morton, Peter (November 26, 1991). "Refining sector kicks off oil recycling effort. (in Canada)". The Oil Daily. Retrieved April 17, 2012. (subscription required)
- Alongi , Paul (GreenvilleOnline.com). "Greenville County hopes to accelerate oil recycling". Retrieved April 17, 2012. Check date values in:
- Swain, Liz (January 1, 2003). "Used Oil Recycling". Environmental Encyclopedia. Retrieved April 17, 2012. (subscription required)
- Harrison, C. (1994). "The engineering aspects of a used oil recycling project". Waste Management. Vol. 14, no. 3-4, pp. 231-235. (subscription required)
- Wolfe, Paris R. (September 1992). "Economics of Used Oil Recycling: Still Slippery" (PDF). Resource Recycling. Retrieved April 17, 2012.
- Johnson, Mackenzie R.; Reynolds, Dr. John G.; Love, Dr. Adam H. (May 2008). "Improving Used Oil Recycling in California" (PDF). California Integrated Waste Management Board, State of California. Retrieved April 17, 2012.
- Recycleoil.org – American Petroleum Institute
- Williams, Christina (April 11, 2012). "New biodiesel hub sets up in Northwest Portland". Sustainable Business Oregon. Retrieved April 17, 2012. External link in
- Energy Efficiency and Recycling at the American Petroleum Institute