Microbial enhanced oil recovery utilizes microorganisms and their metabolic products to improve the oil recovery. A pilot scale study was conducted to investigate the effectiveness of two microorganisms (D-2 and M-1), presenting as an individual and a mixture, by recovering residual oil from a sandstone core oil reservoir at Shengli Oil Reservoir, China. Five microbial flooding tests were conducted sequentially by injecting microbial cultures into the experimental reservoir. The results showed that a polymer surfactant produced by D-2, M-1, and their mixture, enhanced oil recovery by 5.4, 5.6, and 7.9%, respectively, which are within the reported ranges of increased tertiary oil recovery.