We report measurements of the spin torque efficiencies in perpendicularly magnetized Pt/Co bilayers where the Pt resistivity ρPt is strongly dependent on thickness tPt. The dampinglike spin Hall torque efficiency per unit current density ξDLj varies significantly with tPt, exhibiting a peak value ξDLj=0.12 at tPt=2.8-3.9 nm. In contrast, ξDLj/ρPt increases monotonically with tPt and saturates for tPt>5 nm, consistent with an intrinsic spin Hall effect mechanism, in which ξDLj is enhanced by an increase in ρPt. Assuming the Elliott-Yafet spin scattering mechanism dominates, we estimate that the spin diffusion length λs=(0.77±0.08)×10-15 Ω·m2/ρPt. © 2016 American Physical Society.