The 8860 uses 1.5 gal. (5.68 liters) Silicone Oil.
The Bird part number for 1 gallon of silicone oil is 5-1070-2.
For convenience, Bird offers various maintenance kits for the 8860 load that includes the silicone oil here: 8860 Repair & Maintenance Kits
Depending on availability, you can order the oil coolant in a variety of sizes:
|Part Number of Silicone Oil||Container Size|
Please see the Material Safety Data Sheet (SDS) for further information: Silicone Oil SDS