Kyosho SIL500000 Silicone Differential Oil #500000 40cc

Kyosho silicone differential oil in the #500000 grade, supplied in a 40cc bottle.

This is a very heavy oil intended for gear differentials, and gear diff oil weight is one of the most effective tuning tools available on a four-wheel-drive or center-diff car. The thicker the oil, the harder it is for the differential gears to rotate relative to one another, which means the diff gives up less drive under load.

In practice, going heavier locks the axle up more on corner exit and puts power to both wheels rather than letting the unloaded one spin, giving you more forward traction on low-grip surfaces and more stability off throttle into a corner. Going lighter frees the car up and adds steering.

At #500000 this sits at the heavy end of Kyosho's range and is typically used in center differentials, or in the front diff of a car that needs more on-power stability. Silicone oil is used because its viscosity stays stable as the diff heats up over a run, so the car feels the same on the last lap as it did on the first.