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Unburned hydrocarbon (HC) emission results because part of the fuel inducted into the engine escapes combustion. HC emission is dependent on many mechanisms such as adsorption and desorption of fuel in oil layer, flame quenching, fuel escaping into crevices and accumulation of fuel in engine deposits, etc. Out of these, the oil layer adsorption/desorption mechanism contributes to about 25-30% of total engine-out HC emissions. In this work adsorption/desorption mechanism is studied considering the engine to be fueled with different fuels. The fuel adsorbed/desorbed in lubricating oil is modeled with a one-dimensional partial differential equation (PDE). One dimension PDE is chosen as the transverse flow across the oil film is considered to be negligible. The PDE is solved using finite difference explicit scheme in which the space derivatives and the time derivatives are approximated with a second order central difference method and forward Euler method, respectively.