| abstract |
PURPOSE:To obtain the title compsn. which has excellent valve sludge preventive properties, wear resistance, low-temp. solubility, stability in a cooling medium and antiseize characteristics, by blending particular paraffinic and naphthenic base oils with each other. CONSTITUTION:A distillate of a b.p. of 250-450 deg.C obtd. by distilling a paraffinic crude oil is, e.g., hydrogenated and, if necessary, purified by alkali distillation or sulfuric acid washing. Then, the resultant oil is dewaxed with a solvent and, if necessary, hydrogenated, followed by deep dewaxing treatment etc. Thus, a paraffinic base oil (A) having a pour point <=-350 deg.C, a sulfur content <=50ppm and a dynamic viscosity of 5-500cSt (40 deg.C) is obtnd. Subsequently, 2-30wt% naphthenic base oil (B) having a pour point <=-35 deg.C, a sulfur content of 0.05-1wt% and a dynamic viscosity of 5-500cSt (40 deg.C) obtd. by solvent extraction followed by hydrogenating treatment, clay treatment, etc., is blended with 70-98wt% component A and, if necessary, treated with clay. The title compsn. having a sulfur content of 0.01-0.10wt%, is afforded. |