Lubricants are highly value-add petroleum refinery products fabricated from lube base oils, the side cuts from lube-type vacuum towers of crude distillation units. In such a popular lubricant type vacuum distillation unit (LTVDU), the 4th lube side cut, nearby the feeding stage, is normally designed to control the 3rd lube cut end boiling point and the bitumen residue flash point temperature. With useless wider boiling point range than the other lube side cuts, its fate is to discharge as fuel or circulate back to the vacuum furnace for limited higher yield at the cost of more energy. This situation triggered our work to reduce boiling point overlap between the 3rd and 4th lube cuts by implementing dividing wall column (DWC) into LTVDU. This novel design is verified to benefit through an industrial case study. Namely, the 4th lube cut boiling point range is so dramatically narrowed as to be a new lube product, without adding extra heat loads. This way the lube base oil product yield can be greatly improved. Industrially, this DWC designed at LTVDU washing zone can deliver excellent hydraulics and carbon residual controlling performance for larger specific liquid flow by section crossing off for DWC.