  We study a model for an argon-like fluid parameterised in terms of a
hard-core repulsion and a two-Yukawa potential. The liquid-gas phase behaviour
of the model is obtained from the thermodynamically self-consistent
Ornstein-Zernike approximation (SCOZA) of Hoye and Stell, the solution of which
lends itself particularly well to a pair potential of this form. The
predictions for the critical point and the coexistence curve are compared to
new high resolution simulation data and to other liquid-state theories,
including the hierarchical reference theory (HRT) of Parola and Reatto. Both
SCOZA and HRT deliver results that are considerably more accurate than standard
integral-equation approaches. Among the versions of SCOZA considered, the one
yielding the best agreement with simulation successfully predicts the critical
point parameters to within 1%.
