Two methods including furfural refining and dual-solvent (2-Propanol and furfural) refining were investigated respectively in recycling the used industrial lubricating oil. The results show that the performance of dual-solvent refining is better than furfural refining. The optimum process condition is as follows: refining temperature 75 ℃, volume ratio of solvent 2-Propanol to furfural 1∶1, volume ratio of solvent to oil ratio 1.5∶1. Under these optimum conditions, the physical properties[KG*2]of[KG*2]recycled[KG*2]oil is[KG*2]listed[KG*2]as[KG*2]follows:[KG*2]viscosity[KG*2]index[KG*2]119.5,[KG*2]refractive[KG*3]index[KG*3]1.476[KG*3]6,[KG*3]Color[KG*3]1.0,[KG*3]freezing[KG*3]point -15.8 ℃, flash point 218.4 ℃ , sulfur content 0.026%, the total oil yield 72.5%.

The refining of vehicle waste lubricant oil using the furfural as the main solvent and sodium dodecyl benzene sulfonate as the cosolvent were studied. The influence of mixed solvent ratio, extraction temperature and other factors on the yield and quality of recovery refined oil are also investigated. It turns out that when the temperature is 80 ℃, the catalyst oil ratio is 1.5, the additive precentage of sodium dodecyl benzene sulfonate is 0.025%, the properties of refined oil with high yield[KG*3](91.26%)[KG*3]is[KG*3]listed[KG*3]as follows: the viscosity index is 116.83, the refractometer index on 25 ℃ is 1.441, the chromatic is 2.0, the condensation point -19 ℃, w(carbon residue) is 0.496%. The refined lubricated oil after adding some additive can meet the requirements of lubricant oil, and can be reused.

The refining of industrial waste lubricating oil was investigated with N-methyl-2-pyrrolidone (NMP) and Duo-solvent (ethanolamine and NMP) as solvents, respectively. The preferred refining process is duo-solvent refining under 70 ℃ with 5% ethanolamine, under these conditions the total oil yield was 89.85%. The physical properties of recycled oil is listed as follows: viscosity（40 ℃） 30.89 mm ²•s ^-1, viscosity（100 ℃） 5.6 mm ²•s ^-1, viscosity index 120.4, refractive index 1.450, Color 2.0, freezing point -28.8 ℃, flash point 219.6 ℃ and sulfur content 0.057%.

Di-solvent is composed with epichlorohydrin and furfural. Two methods of furfural and di-solvent were investigated in recycle the used lubricating oil for effects. The experimental results show that the optimal technology conditions of di-solvent refining are the volume ratio of oxidant to oil 1.0 and V(epichlorohydrin)∶V(furfural) 1.5∶1. The optimal technology condition of furfural refining is the volume ratio of oxidant to oil 1.5 .Under the optimal technology conditions, the used engine oil total yield reach 73.95%. The properties of the recovered oil are viscosity index at 118.4, after append to a process of clay-adsorption, the recovered oil could be circularly used by harmonicing of proper quantities additions.