  A widely used method for parameterizing the outcomes of common envelopes
(CEs) involves defining an ejection efficiency, $\bar{\alpha}_{\mathrm{eff}}$,
that represents the fraction of orbital energy used to unbind the envelope as
the orbit decays. Given $\bar{\alpha}_{\mathrm{eff}}$, a prediction for the
post-CE orbital separation is possible with knowledge of the energy required to
unbind the primary's envelope from its core. Unfortunately, placing
observational constraints on $\bar{\alpha}_{\mathrm{eff}}$ is challenging as it
requires knowledge of the primary's structure at the onset of the common
envelope phase. Numerical simulations have also had difficulties reproducing
post-CE orbital configurations as they leave extended, but still bound,
envelopes. Using detailed stellar interior profiles, we calculate
$\bar{\alpha}_{\mathrm{eff}}$ values for a matrix of primary-companion mass
pairs when the primary is at maximal extent in its evolution. We find that the
ejection efficiency is most sensitive to the properties of the surface-contact
convective region (SCCR). In this region, the convective transport timescales
are often short compared to orbital decay timescales, thereby allowing the star
to effectively radiate orbital energy and thus lower
$\bar{\alpha}_{\mathrm{eff}}$. The inclusion of convection in numerical
simulations of CEs may aid ejection without the need for additional energy
sources as the orbit must shrink substantially further before the requisite
energy can be tapped to drive ejection. Additionally, convection leads to
predicted post-CE orbital periods of less than a day in many cases, an
observational result that has been difficult to reproduce in population studies
where $\bar{\alpha}_{\mathrm{eff}}$ is taken to be constant. Finally, we
provide a simple method to calculate $\bar{\alpha}_{\mathrm{eff}}$ if the
properties of the SCCR are known.
