Preconditioning strategies for elliptic partial differential operators and their discrete counterparts are compared by a model problem. The technique uses a selfadjoint positive definite operator \(B\) as the preconditioner for the nonselfadjoint convection-diffusion operator \(A\). Preconditioning is done by \(A\)'s leading term plus a positive zeroth order term of the form \(\delta I\). The optimal value of \(\delta\) is also examined.