  Wilson coefficients of light four-quark condensates in QCD sum rules are
evaluated for pseudo-scalar $D$ mesons, thus, pushing the sum rules toward mass
dimension six. Contrary to the situation for $\bar{q}q$ mesons the impact of
the four-quark condensates for vacuum as well as in-medium situations is found
to be rather small within the Borel window used in previous analyses. The
complete four-quark condensate contributions enable to identify candidates for
an order parameter of spontaneous chiral symmetry breaking/restoration as well
as to evaluate stability criteria of operator product expansions.
