I was wondering if I could build a filtration system to recycle my own waste oil, if so what would the investment be? I was thinking two small drums, the first as a settlement tank and the second to filter the oil.
You will need a centrifuge to filter out the impurities and end with clean oil. It would be very costly. When I was in the CG we had a centrifuge to clean the oil but the engines used quite a few 55 gal drums in total.