The role of clay in reservoirs and its possible influence oil kinetics of crude oil burning is not entirely clear However, it is known that (1) clay fractions of the reservoir matrix possess the highest surface area per gram, (2) clay fractions are the most chemically reactive of the inorganic constituents present in the reservoir and (3) clay minerals generally possess catalytic properties toward various organic liquids. This study was aimed to investigate the role of clay on thermo-oxidative behavior of crude oil at different clay contents in limestone medium. To do this, lion-isothermal kinetic experiments were conducted in a reaction cell by injecting 1.5 lt/min of air into the cell having matrix containing limestone (92% calcite, 66% doloinite and 1.4% quartz) with 0, 5 and 10% addition of clay (kaolin). The pre-combustion and combustion behavior of Batt Raman (12.9 degrees API gravity) crude oil from south-east Turkey was studied by using continuous analysis of produced gases. Clay content of the matrix influenced the amount of the fuel deposited oil the limestone. More fuel was increasingly deposited as the clay content was increased. Addition of clay also increased the combustion peak temperature. This call be attributed to the (1) or (3) of the preceding section. Results also indicate that the average molar CO2/CO ratio increased from 3.71 to 5.97 upon addition of 10% clay to the limestone. Finally, a uniform trend of decreasing activation energies as well as the Arrhenius constants by addition of clay to the limestone was observed. It was concluded that clay's large surface area affects the values of Arrhenius constant, while it is the catalytic properties of clay that lower the activation energies of all three major reactions (i.e., low temperature oxidation, fuel deposition and fuel combustion) involved in the in-situ combustion process.