A high pressure shock tube "HPST" has been designed and validated for the purpose of chemical kinetics studies at elevated pressures and temperatures. Using this facility, auto-ignition investigations are conducted for methane at 10, 20 and 40 bar and temperatures from 1400 K up to 2000 K. Three equivalence ratios (phi = 0.5, 1 and 2) for a methane/oxygen/argon mixture were studied in this paper under diluted conditions (argon > 90%). Experimental data showed good agreement with previous literature measurements and predictions from three different chemical kinetic models (Aramco Mech 1.3, USC Mech II and GRI Mech 3.0) commonly used in the literature, which confirms the quality of the experimental data obtained with the new high pressure shock tube and allows the expansion of the validation range of the mechanisms for ignition delay times to higher pressures. The investigations performed to explain the differences observed for ignition delay times predictions highlighted an important sensitivity of the USC mechanism predictions to equivalence ratio and an important sensitivity to CH3 + O-2 reactions. Finally, the impact of pressure and equivalence ratio on ignition delay time is evaluated over a broad range of pressure (1-50 bar) and equivalence ratio (phi = 0.2-3). (C) 2016 Elsevier Ltd. All rights reserved.