One low-cost improved oil recovery (IOR) technology making significant advances is reservoir flooding with thermophilic microbes. The gram-negative cells of the Thermus SP3 strain were grown at high temperatures up to 85degrees C in the neutral to alkaline pH range. Depending on the culture conditions, the organism occurred as single rods, or as filamentous aggregates. Thermus SP3 was grown chemoorganotrophically and produced volatile fatty acids, 4-hydroxy-4-methyl-2-pentanone, xylene, undecane, 1,2-benzenedicarboxylic acid, bis (2-methylprophl) ester, dibutyl phthalate, di-n-octyl phthalate and surfactants, which had various effects on crude oil. Thermus SP3 could decrease the viscosity and paraffin content of crude oil, degrade heavy fractions, increase the content of light compositions of crude oil, improving the physical and chemical properties, and improve oil recovery (12.59%). Thermophilic Thermus SP3 strain was screened to begin optimizing the process and core-flood was performed to quantify oil recovery. A laboratory core-flood experiment using microbial flooding methodology showed that oil recovery was better than with chemical flooding oil recovery.