Two combustible mixtures, H-2-O-2-Ar and H-2-O-2-N-2, are widely used in detonation research, but only the latter has been employed in oblique detonation wave (ODW) studies. In this study, ODWs in H-2-O-2-Ar are simulated to investigate their structural characteristics using reactive Euler equations with a detailed chemistry model. Similar to ODWs in H-2-O-2-N-2 mixtures, two observed structures are dependent on incident Mach numbers. However, in mixtures of 2H(2 )+ O-2 + 7Ar, the structures are sensitive to inflow static pressure P-o, different from the structures in H-2-O-2-N-2 mixtures. Based on flow field analysis, the ratio of induction and heat release zone lengths R-L is proposed to model the difference induced by dilution gas. Generally, R-L is large in N-2 diluted mixtures but small in Ar diluted mixtures. Low R-L indicates that induction is comparable with the heat release zone and easily changed, resulting in pressure-sensitive structures. When the dilution gas changes gradually from N-2 to Ar, the ratio R-L increases slowly at first and then declines rapidly to approach a constant. The variation rule of R-L is analyzed and compared with results from calculations of a constant volume explosion, demonstrating how different dilution gases influence ODW structures.