<p>The price hiking and depletion of natural asphalt binder resources has motivated the researchers to find alternative approaches. Utilization of waste engine oil (WEO) as partially substitute for asphalt binder can solve the WEO disposal issue and decreasing the dependency on non-renewable binder material. This work evaluated the impact of waste engine oil modifier (WEOM) on physical, rheological, phase separation and chemical properties of asphalt binder. The waste engine oil (WEO) was first pre-modified with Styrene-Butadiene-Styrene (SBS) at SBS: WEO (40:60) ratio to transform into semi-solid material. The asphalt binder of penetration grade 60/70 was blended with five various concentrations of WEOM (2%, 4%, 6%, 8% and 10%). The findings indicated that penetration was decreased while softening point and rotational viscosity enhance with increasing the concentration of WEOM. The temperature susceptibility was also reduced described by the higher penetration index (PI) value. Moreover, the complex shear modulus (G*) and rutting factor (G*/Sin δ) has been increased while phase angle (δ) has shown declination. The improvement in rutting factor (G*/Sin δ) was reflected in the high-temperature performance grade improvement of PG-76 with 8% and 10% WEOM content as compared to base binder of PG-64. Multiple stress creep recovery test further validated the superior performance as indicated by decreased non-recoverable creep compliance (J_nr) and higher recovery for modified asphalt binder. Storage stability test described that the WEOM up to 8% has shown no phase separation issue. Fourier Transform Infrared Spectroscopy showed that only physical reaction takes place between the WEOM and asphalt binder. Based on the physical, rheological and storage stability, 8% WEOM has exhibited most balanced performance and was therefore identified as the optimum dosage.</p>