The coadsorption of CO and butane on a Pt(533) stepped surface has been investigated using reflection absorption infrared spectroscopy (RAIRS) and temperature programmed desorption (TPD). The adsorption of butane on Pt(533) with CO preadsorbed on step-atop sites reveals that butane can force CO to tilt with a minimum angle of 42 degrees away from the surface normal and displace CO from step-atop to step-bridge sites. The energy required for this tilting should be less than 20.5 kJ/mol. The coverage at which the compressed butane phase occurred was found to be the same at which this phase occurs on bare Pt(533). Together with the observed tilting and displacement of CO, this suggests that at low coverages butane adsorbs on the terraces, rotated 60 degrees away from the step edge. The second monolayer phase then consists of tilted butane molecules having two hydrogen atoms in direct contact with the surface, situated near the step edge. The presence of butane also results in a downward shift of the CO stretch frequency, caused by electron donation in the 2 pi* antibonding CO orbital. When butane is preadsorbed at a submonolayer coverage exposure to CO leads to displacement of butane into a compressed phase and even into a multilayer phase. This effect becomes smaller as the initial butane coverage is increased to the multilayer regime.