diff --git a/src/equations/compressible_navier_stokes_1d.jl b/src/equations/compressible_navier_stokes_1d.jl
index 94135d346d7..5d09bc1f587 100644
--- a/src/equations/compressible_navier_stokes_1d.jl
+++ b/src/equations/compressible_navier_stokes_1d.jl
@@ -21,6 +21,8 @@ the [`CompressibleEulerEquations1D`](@ref).
 
 Fluid properties such as the dynamic viscosity ``\mu`` can be provided in any consistent unit system, e.g.,
 [``\mu``] = kg m⁻¹ s⁻¹.
+The viscosity ``\mu`` may be a constant or a function of the current state, e.g., 
+depending on temperature (Sutherland's law): ``\mu = \mu(T)``.
 
 The particular form of the compressible Navier-Stokes implemented is
 ```math
@@ -160,13 +162,14 @@ function flux(u, gradients, orientation::Integer,
     # in the implementation
     q1 = equations.kappa * dTdx
 
-    # In the simplest case, `mu(u, equations)` returns just a constant but
+    # In the simplest cases, the user passed in `mu` or `mu()` 
+    # (which returns just a constant) but
     # more complex functions like Sutherland's law are possible.
     if equations.mu isa Real
         mu = equations.mu
+    else
         # The equations are equipped with a function that computes the dynamic viscosity mu
         # from the current state. 
-    else
         mu = equations.mu(u, equations)
     end
 
diff --git a/src/equations/compressible_navier_stokes_2d.jl b/src/equations/compressible_navier_stokes_2d.jl
index 40c681ca9b7..48b68223a60 100644
--- a/src/equations/compressible_navier_stokes_2d.jl
+++ b/src/equations/compressible_navier_stokes_2d.jl
@@ -21,6 +21,8 @@ the [`CompressibleEulerEquations2D`](@ref).
 
 Fluid properties such as the dynamic viscosity ``\mu`` can be provided in any consistent unit system, e.g.,
 [``\mu``] = kg m⁻¹ s⁻¹.
+The viscosity ``\mu`` may be a constant or a function of the current state, e.g., 
+depending on temperature (Sutherland's law): ``\mu = \mu(T)``.
 
 The particular form of the compressible Navier-Stokes implemented is
 ```math
@@ -169,13 +171,14 @@ function flux(u, gradients, orientation::Integer,
     q1 = equations.kappa * dTdx
     q2 = equations.kappa * dTdy
 
-    # In the simplest case, `mu(u, equations)` returns just a constant but
+    # In the simplest cases, the user passed in `mu` or `mu()` 
+    # (which returns just a constant) but
     # more complex functions like Sutherland's law are possible.
     if equations.mu isa Real
         mu = equations.mu
+    else
         # The equations are equipped with a function that computes the dynamic viscosity mu
         # from the current state. 
-    else
         mu = equations.mu(u, equations)
     end
 
diff --git a/src/equations/compressible_navier_stokes_3d.jl b/src/equations/compressible_navier_stokes_3d.jl
index 6e99fb630e5..be80360288e 100644
--- a/src/equations/compressible_navier_stokes_3d.jl
+++ b/src/equations/compressible_navier_stokes_3d.jl
@@ -21,6 +21,8 @@ the [`CompressibleEulerEquations3D`](@ref).
 
 Fluid properties such as the dynamic viscosity ``\mu`` can be provided in any consistent unit system, e.g.,
 [``\mu``] = kg m⁻¹ s⁻¹.
+The viscosity ``\mu`` may be a constant or a function of the current state, e.g., 
+depending on temperature (Sutherland's law): ``\mu = \mu(T)``.
 
 The particular form of the compressible Navier-Stokes implemented is
 ```math
@@ -182,13 +184,14 @@ function flux(u, gradients, orientation::Integer,
     q2 = equations.kappa * dTdy
     q3 = equations.kappa * dTdz
 
-    # In the simplest case, `mu(u, equations)` returns just a constant but
+    # In the simplest cases, the user passed in `mu` or `mu()` 
+    # (which returns just a constant) but
     # more complex functions like Sutherland's law are possible.
     if equations.mu isa Real
         mu = equations.mu
+    else
         # The equations are equipped with a function that computes the dynamic viscosity mu
         # from the current state. 
-    else
         mu = equations.mu(u, equations)
     end