Any petroleum-based oil in a hydraulic clutch system is a disaster waiting to happen, as the oil atttacks the rubber parts and makes them swell up and blow out. If it is actually oil in there, I'd replace or rebuild everything, master cylinder, slave cylinder, and any flex lines in the circuit. At least flush everything out with alcohol, followed by a fill with fresh DOT 3 or 4 fluid, then bleed the system thoroughly. Nothing like pushing the clutch pedal, and not being able to get that beast out of gear!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!