my memory is fuzzy but i think that i read that when Dodge put the electric fan helper unit on the 4.7v8 version, they then filled the viscous clutch with a lower viscosity silicone fluid that allowed the fan to slip at a lower rpm

there should be a fuel economy gain
especially at idle during weather cool enough
to keep the electric fan off

i have an Oztrip brand fuel consumption meter on my 5.9v8 that measures gallons per hour at idle
i remember that it is about 0.65 fully warmed up
and 0.75 with AC on

i have run without fan blades but cant remember what the idle consumption dropped to right off

Silicone brake fluid is perhaps the easiest fire resistant fluid commonly found.
Perhaps its viscosity is lower than common factory fill of Dodge viscous clutches?

if it is one could blend a fluid to bring the RPM down to custom levels....