Both technologies are in use. ... Published June 30, 2018 06:41 by Rafael Gay-de-Montella MSc PEng, Water Wastewater Treatment Expert, Oil-Gas, Tailings, Boilers, ZLD; Evaporators, Sludge Both technologies are in use. For Crude separation (sp. HO crude extraction) designers tend to go API. For light Oils CPI could be more efficient (and less costly).