  We investigate the influence of both a new generation of low-temperature
opacities and of various amounts of alpha-element enhancements on stellar
evolution models. New stellar models with two different alpha-element mixtures
and two sets of appropriate opacity tables are computed and compared. The
influence of the different mixtures as well as that of the improved generation
of opacity tables is investigated. It is found that around solar metallicity
the new opacity tables have a drastic influence on stellar temperatures, which
is mainly an effect of the new low-temperature tables, and not of variations in
alpha-element enhancement factors. The latter, however, influence stellar
lifetimes via systematic opacity effects at core temperatures. We trace the
reason for the low-temperature table changes to errors in the old tables. We
conclude that variations in alpha-element abundance ratios affect the
main-sequence properties of super-solar metallicity stars significantly. Red
giant branch effective temperatures depend only slightly on the specific
mixture. Our older low-temperature opacity tables were shown to be erroneous
and should no longer be used for stellar models with near- or super-solar
metallicity. Corrected tables have already been produced.
