Silicone oil for filling differentials with a density of 25000 cSt. The operation of the differential is to maintain the speed difference between the outer and inner wheel when cornering. This prevents the constant slipping of one of the wheels that would be caused by the same speed of wheels that travel on different road lengths. The outer wheel always travels a longer distance than the inner wheel when cornering, and the lack of speed differentiation leads to a constant slipping of a wheel, preventing proper control of the vehicle. For example, on an off-road track, a higher density silicone oil (viscosity) is often used, and on smooth, grippy tracks, a lower density is used, which in this case allows a more natural glide and better control of the vehicle.