  Based upon the intrinsic symmetries approach to inhomogeneous cosmologies, we
propose an exact solution to Einstein's field equations where the spatial
sections are flat and the source is a non-perfect fluid such that the
dissipative terms can be written in terms of spatial gradients of the energy
density under a suitable choice of the coordinate system. It is shown through
the calculation of the luminosity distance as a function of the redshift that
the presence of such inhomogeneities may lead to an effective deceleration
parameter compatible with either the standard $\Lambda$CDM model or LTB models
depending on the choice of boundary conditions with no exotic matter. This fact
is another evidence that different inhomogeneous models should be carefully
investigated in order to verify which model may be compatible with observations
and still be as close as possible to the standard model regarding the
underlying assumptions, without resorting necessarily to exotic matter
components.
