Abstract <p>The depletion of low-viscosity crude oil reserves necessitates the production of heavy, high-viscosity crude oil. However, transportation of heavy oils is challenging due to their high viscosity. This study aims to develop a sustainable solution to reduce the viscosity of heavy oil by exploiting oscillating bubbles within the fluid. This is because traditional methods by drag reduction additives cause environmental pollution and dangerous emissions, in addition to their high economic cost. An ultrasonic device with a constant power of 150 W and a frequency of 40 kHz was used at different temperatures, while the ultrasonic irradiation time was 10 and 15 min. A viscosity reduction rates (VRR) factor was used to determine changes in viscosity. The viscosity reduction rate (VRR) was at its best at an irradiation time of 10 min under the present experimental conditions and at different temperatures, where it reached more than 36%. At 70°C, when the irradiation time reached 15 min, the viscosity of the oil samples increased. The results indicate that the cavitation, thermal, and mechanical effects of ultrasound can break the long carbon chains of crude oil and form short chains, thus reducing the viscosity. The increase in viscosity after increasing the irradiation time can be attributed to the re-association between molecules. The technique is promising as an eco-friendly and efficient method for heavy oil viscosity reducing alternative that reduces chemical usage and preventing carbon emissions.</p>