This paper considers the impact of the parameterization of subgridscale mixing on ocean heat transport in coarse-resolution ocean models of the type used in coupled climate models. Increasing the vertical diffusion increases poleward heat transport in both hemispheres. Increasing lateral diffusion associated with transient eddies increases poleward heat transport in the southern hemisphere while decreasing it in the northern hemisphere. The results are interpreted in the context of a simple analytical model.