Low-shear viscosities were measured of dilute aqueous dispersions of charged boehmite rods with an average aspect ratio of 22.5 as a function of the Debye length kappa(-1) and the particle volume fraction Phi. It is found that the low-shear viscosity of the dispersions scales with the effective overlap concentration v/v(1)*, where v(1)* is the minimum overlap concentration of rods with an effective length L* = L + 5(kappa)(-1). This dynamic scaling is also valid for low-shear viscosity data of FD-virus solutions (Graf et al. J. Chen. Phys. 1993, 98, 4920). The rescaled relative viscosity curves can be described by the (Maron-Pierce) equation eta(r) = (1 -(v/v(1)*)/(v/v(1)*)(max))(-2). The effective overlap concentration at which the low-shear viscosity diverges, (v/v(1)*)max, is much lower for the boehmite rods than for the semiflexible FD-virus and hard rods without electric double layers. Extrapolation of the reduced viscosity to v/v(1)* = 0 yields an unrealistic high intrinsic viscosity [eta]. Possibly the relative viscosity of dilute dispersions at very low ionic strength shows a nonanalytical concentration dependence, which renders the definition of [eta] for colloids with thick double layers questionable.