A magnetorheological (MR) fluid includes a hydrocarbon carrier fluid. The MR fluid further includes magneto-responsive particles within the hydrocarbon carrier fluid, the particles having a size distribution with a maximum size less than about 100 microns. A clay-based suspending agent is disposed within the hydrocarbon carrier fluid. In an embodiment, the magneto-responsive particles may be ferromagnetic particles, and may be distributed in a suitable size distribution pattern, such as, for example, a bimodal distribution or the like.