The authors present multigrid solvers for convection-diffusion equations in two-dimensional domains. These equations are discretized by a fourth-order finite difference scheme based on a nine-point stencil. Multigrid algorithms with Gauss-Seidel smoother with different orderings (lexicographical, red-black, symmetric horizontal line, alternating zebra) and different intergrid transfer operators (full-injection, full-weighting) are compared. The numerical examples show that the multigrid algorithm with red-black Gauss-Seidel smoother and injection as restriction operator is efficient and cost effective. Furthermore, one can observe for fixed convection parameters that the multigrid convergence rate is independent of the discretization parameter and of the diffusion parameter.