This design is made from 100% pure silicone oil and will not be thin in hot weather and thick in cold weather. The thicker the oil, the less your differential will "diffuse out" in the corners where the two tires spin at different speeds.
Ultimate RC Silicone Oil 40,000 cps # 75ml
Ultimate RC silicone spray hose HI-RESISTANCE black 2.5x6mm 1 meter
SILICONE OIL DIFFERENTIAL GRADE 100000 BOTTLE 100ml SILICONE OIL HIMOTO
Traxxas Silicone Oil Premium Shock Absorber 80WT 1000cst 60cc TRX5037
Mugen Silicone Oil for Differentials 7,000 (7000) - B0323
Ultimate RC Multibox with Lockable Lid 365x295x85 Sorting Box