  We have revisited the sdB+K-star long-period binary PG 1018-047 based on 20
new high-resolution VLT/UVES spectra that provided regular coverage over a
period of more than 26 months. We refine the period and establish that the
orbit is significantly eccentric ($P=751.6\pm1.9\rm{d}$ and $e=0.049\pm0.008$).
A simultaneous fit derived from the narrow metal lines visible in the spectrum
of the sdB star and the metal lines in the red part of the spectrum that
originate from the companion provides the mass ratio, $M_{\rm MS}/M_{\rm sdB} =
1.52 \pm 0.04$, for the system. From an NLTE model atmosphere analysis of the
combined spectra, we find $T_{\rm eff}$=29900$\pm$330K, log$g$=
5.65$\pm$0.06dex and log($n_{\rm He}$/$n_{\rm H}$)=-3.98$\pm$0.16dex for the
primary, consistent with a B-type hot subdwarf star. The spectral contribution
of the companion is consistent with a K5V-type star. With the companion having
a mass of only $\sim$0.7$\rm M_{\odot}$ this system lies close to the boundary
below which stable Roche-lobe overflow (RLOF) cannot be supported. To model the
evolution of such a system, we have extended earlier MESA models towards lower
companion masses. We find that both phase-dependent mass loss during RLOF, when
30 to 40\% of the available mass is lost through the outer Lagrange point, and
phase-dependent mass loss during RLOF in combination with a circumbinary disk
of maximum $M_{\rm CB} = 0.001\rm M_{\odot}$ could have formed the PG1018-047
binary system.
