In this study, we evaluated three types of stabilizers for preventing oil layer formation and particle sedimentation in magnetorheological fluids (MRFs). Stabilizer dispersion and dissolutions were characterized by rheological measurements of mineral oil and MRF. Centrifugal stability tests were also conducted for MRFs containing the stabilizers. We found that the relationship between the non-Newtonian flow index and the concentration of stabilizers in the oil was similar to that in the MRFs. In addition, we found that a suitable degree of internal structure created a sufficiently stable MRF that also exhibited sufficient fluidity.