During the last few years, the control of motor vehicles pollution has generated considerable research oriented towards the efficiency and the yield of the combustion techniques. A relatively new technology based on the plasma treatment of inlet gases appears to improve the operating conditions of internal combustion engines. The primary focus of this technique is the transformation of methane–air mixture into hydrogen-rich gas before the admission in the cylinder of the vehicle engine. This work describes an experimental investigation in CH4–air mixture using a 20 kHz sliding discharge plasma reactor at atmospheric pressure. After plasma treatment, the major gaseous: H2, CH4, CO, CO2 and H2O were analyzed and quantified using a micro-gas chromatograph (GC) and Fourier transform infrared absorption spectrometer (FTIR). Plasma treatment results show H2 enrichment in the range of 4–10% of the inlet gas mixture.