Different blends containing 5%, 10%, 15%, 20%, 25%, and 30% of polyalphaolefin-100 (PAO-100) as a minor component and solvent neutral-150 (SN-150) as a major component were prepared. The important lubrication properties of the blends were then measured. The obtained results indicate that upon increasing the weight percentage of PAO-100, the viscosity index (VI) rises, the cold cranking simulator (CCS) diminishes, and viscosities approach the corresponding values due to solvent neutral-500 (SN-500). Different equations were derived between the viscosity and VI and weight percentage of PAO-100. A similar procedure was employed for blends containing 1%, 5%, 10%, 12%, and 15% of polyisobutene (PIB). In this case, results parallel to PAO-100 were obtained. The 30% PAO-100: SN-150 and 12% PIB: SN-150 mixtures were successfully employed for the equalization of semisynthetic engine oil SAE 20W50 API SJ from Millers Company. Biodegradability as well as tribotests were performed on the recent blends and compared with corresponding values due to SN-150.