According to this table, per-fluorocarbons like CF4 are slightly more polarizable than analogous hydrocarbons like CH4 (2.824 vs 2.448). However, polarizability is measured under uniform electric field which is never encountered in reality. Instead, molecules carry only tiny amounts of dipole moment. Because the dipole field decays quickly with distance, the induced dipole interaction should be highly sensitive to distance. Considering that per-fluorocarbons are substantially bigger but have similar polarizability, their interaction should be much weaker than hydrocarbons. This paper also claims that per-fluorocarbons interact much more weakly with hydrocarbons, which is why they don’t mix despite both being nonpolar.