NONE 20260504105603227 wseas/wseas content-registration-form+ja@crossref.org content-registration-form WSEAS TRANSACTIONS ON FLUID MECHANICS 1790-5087 2224-347X Ortenca Gropa Department of Energy Resources, Faculty of Geology and Mining, Polytechnic University of Tirana, Tirana, ALBANIA Erison Karamani Department of Energy Resources, Faculty of Geology and Mining, Polytechnic University of Tirana, Tirana, ALBANIA Heavy crude oil production remains challenging mainly because of its high viscosity and complex non-Newtonian flow behaviour, which can reduce reservoir performance. Under these conditions, conventional recovery methods are often insufficient, necessitating enhanced oil recovery (EOR) techniques. This study focuses on the use of diluents, which reduce viscosity and improve production efficiency. Laboratory measurements under surface conditions indicate viscosity reductions of 50–99%, depending on diluent concentration and temperature. This paper examines diluent injection in the Visoka oilfield, Albania—a field with high-viscosity, non-Newtonian crude. The injection of light hydrocarbons alters the crude oil’s rheological behaviour, allowing easier flow near the wellbore and during surface handling, while also contributing to reservoir pressure maintenance. Similar behaviour has been observed in other heavy oil fields. The results from the Visoka oilfield indicate higher recovery rates and improved well performance. Further investigation under reservoir conditions could help refine these strategies. 12 31 2025 12 31 2025 198 20 https://creativecommons.org/licenses/by/4.0/deed.en_US 10.37394/232013.2025.20.20 https://wseas.com/journals/fluids/2025/a405113-418.pdf C. Temizel, C. H. Canbaz, M. Tra, E. Abdelfatah, B. Jia, D. Putra, M. Irani, A. 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