Parker's highly fluorinated high performance fluoroelastomer (HiFluor?) O-rings are very compatible with hydraulic oil and fuels....
Parker's perfluorelastomer (Ultra? FFKM) O-rings are very compatible with hydraulic oil and fuels....
Parker's fluorocarbon (FKM, FPM) O-rings are compatible with oils and gases, hydraulic oil and fuels....
Parker's ethylene propylene rubber (EPM, EPR, EPDM) O-rings are compatible with solvents and other chemicals....
Parker's hydrogenated nitrile (HNBR, HSN) O-rings are very compatible with oils and gases....