Kind of a short, oddball post here, but I thought it might be of use/interest to someone. Also, it’s probably easier for me to find it if it’s here. I stumbled upon a translated excerpt of the T-14’s manual, and here are the capacities for the fuel/oil/cooling systems:

Fuel System
Internal (under the armor) tanks: 860 L
External (outside armor): 755 L
Total nominal fuel capacity: 1,615 L

Like most Russian tanks, the Armata can mount a pair of 200 L drums on brackets aft. Therefore:
Fuel capacity with supplemental tanks: 2,015 L

Engine oil tank capacity: 80 L

Cooling system capacity: 125 L
(including heat exchangers)

Transmission hydraulic fluid capacity: 90 L

Gearbox hydraulic capacity: 20 L