  Gluon and ghost propagators data, obtained in Landau gauge from lattice
simulations with two light and two heavy dynamical quark flavours
($N_f$=2+1+1), are described here with a running formula including a four-loop
perturbative expression and a nonperturbative OPE correction dominated by the
local operator $A^2$. The Wilson coefficients and their variation as a function
of the coupling constant are extracted from the numerical data and compared
with the theoretical expressions that, after being properly renormalized, are
known at ${\cal O}(\alpha^4)$. As also $\Lambda_{\msbar}$ is rather well known
for $N_f$=2+1+1, this allows for a precise consistency test of the OPE approach
in the joint description of different observables.
