Yokomo RP-113375 RP Ultra Shock Oil #37.5 (Purple) - 40cc Silicone Shock Oil for R/C  [RP-113375]

Overview of RP Ultra Shock Oil

The Yokomo RP-113375 RP Ultra Shock Oil #37.5 is a silicone-based shock fluid packaged in a 40cc bottle and marked purple to aid identification. The RP Ultra range was adjusted to provide finer viscosity increments so drivers and tuners can better match damping characteristics without swapping components.

Its role is exclusive damping control: it governs piston flow and rebound rates within R/C shock bodies. Employ it to adjust compression and rebound behaviour during suspension setup, particularly when you need small, repeatable changes between runs. The purple coding makes this viscosity easy to find among other bottles.

For standard threaded shock bodies the procedure is simple: drain old oil, clean the parts, refill to the specified level for your shock design, then compress repeatedly to remove entrained air and seat the piston. Keep your filling process consistent and check for foam before completing the rebuild.