Contrary to popular belief, when motor oil becomes ‘used’ it’s not actually the oil that degrades in quality, but the additives within the oil. The oil refining process takes the dark odiferous crude oil, and refines it into the motor oil we use in engines. Through a similar process, we can also take used oil, remove the grit, combine additives, and allow it for reuse. The additives that go into motor oil are essential for preserving the quality of the engine. For example, if you were refining bulk outboard motor oil, you would need to combine additives that prevent water from entering the motor oil.
Re-refining is a newer process that became popular when oil recycle stations became popular in hardware stores, auto stores, and marinas. Through re-refining, people can conserve fossil fuels, and also help the environment. As oil prices continue their rollercoaster ride on the market, methods to use less oil will become much more important.