Abstract Nowadays, in our modern daily life, car-washing stations play a great role. Car-washing stations are among the activities that consume large capacities of fresh water on daily basis. Oil-contaminated wastewater can have a detrimental effect on municipal biological treatment processes. Fenton's reagent; one of the advanced oxidation processes (AOPs) has been applied in this study. The experiments were planned and conducted according to the factorial Box-Behnken design based on the experimental surface methodology to treat a real car washing wastewater. Lab-scale experiments with UV source, coupled with Fenton's reagent, suggested the hydrocarbon oil is readily degradable. Moreover, the Fenton dose was optimized and the COD is maximized to reach to more than 93% removal after only one hour of reaction time. The optimum Fenton's reagent dose is 48.4 and 403.9 mg/L for Fe2+ and H2O2, respectively. However, the optimum pH is 3.5.