I found this when researching whether to use silicone or EDPM gaskets on my sanitary fittings:
"Silicone rubber has outstanding resistance to oil at high temperatures. Among common organic rubbers, nitrile rubber and chloroprene rubber have somewhat higher oil resistance at temperatures below 100°C, but at higher temperatures silicone rubber is superior. Silicone rubber also has excellent resistance to solvents and other chemicals. It is essentially unaffected by polar organic compounds (aniline, alcohol, etc.) or dilute acids or bases, with the increase in volume due to swelling in the range of only 10%–15%. Silicone rubber does swell in non-polar organic compounds like benzene, toluene and gasoline; but unlike most organic rubbers, it does not decompose or dissolve, and will return to its former state when the solvent is removed. Silicone rubber is, however, adversely affected by strong acids and bases, so it should not be used where it will come in contact with such chemicals.
Typically, the effects of solvents on silicone are evidenced by the swelling, softening and reduced strength of the rubber; the extent of these effects depends on the type of solvent involved."
This was found on page six of this report: http://www.silicone....df/rubber_e.pdf