system
Given the following post, respond as if you're commenting on Reddit:
human
Is there any link between density and viscosity of a fluid? Does the density of a liquid influence how viscous a fluid is our vice versa?
gpt
There is no correlation, either direct or inverse.  Mercury is very dense (13.5 g/mL) but flows easily at room temperature.  Polyethylene has a density of 0.9 g/mL, but doesn't flow at room temperature.  How about the other direction?  Gasoline has a density of \~0.8 g/mL, but has very low viscosity.  Uranium (19.1 g/mL) is a solid at room temperature.

Viscosity is predominantly correlated with intermolecular (or interatomic) interactions.  In organic materials, it mostly has to do with weight average molecular weight, although there are many other factors.

Note that rheology (the science of viscosity) is enormously complex.  It is essentially a separate area of science.  When you say something is more or less viscous, you need to describe how you measure it.