  We perform linear stability analyses (LSA) and direct numerical simulations
(DNS) to investigate the influence of the dynamic viscosity on viscous
fingering (VF) instability in miscible slices. Selecting the characteristic
scales appropriately the importance of the magnitude of the dynamic viscosity
of individual fluids on VF in miscible slice has been shown in the context of
the transient interfacial tension. Further, we have confirmed this result for
immiscible fluids and manifest the similarities between VF in immiscible and
miscible slices with transient interfacial tension. In a more general setting,
the findings of this letter will be very useful for multiphase viscous flow, in
which the momentum balance equation contains an additional stress term free
from the dynamic viscosity.
