Nitrile should be fine, Viton is much better.
The following info on some of the commonly used gasket / o-ring materials might be useful
Natural Rubber 110 C Max Temp.
Good Mechanical Properties.
Resistant to Water.
Fair to good resistance to acids and alkalis.
Poor resistance to oils petrol.
Poor Resistance to Weathering.
Butyl 150 C Max Temp.
Very good resistance to water, alkalis, many acids.
Poor resistance to oils, petrol, and most solvents.
Nitrile 150 C Max Temp.
Very good resistance to water.
Fair resistance to alkalis, acids.
Excellent resistance to oils and petrol.
Neoprene120 C Max Temp.
Good resistance to water and alkalis, fair resistance to acids.
Good resistance to non-aromatic pertroleum, fatty oils, solvents
(except aromatic, chlorinated or ketone types).
Excellent mechanical Properties
Viton/Fluoroelastomer 230 C Max Temp.
Good Mechanical properties
Excellent resistance to ozone weathering.
Can be used at high temperatures with with many fuels, lubricants, hydraulic fluids, solvents.