Quote Originally Posted by DBP
If there is no oil on the lens itself, then don't worry. Oil is mainly a problem on SLRs, where the aperture blades have to move very quickly and oil slows that action. On an enlarger, or rangefinder for that matter, the only issue is potential migration, which tends to be very slow.
One concern that just came to mind is the effect of heat (from the enlarger) on the oil. I wonder how likely it is for the oil to evaporate, due to the heat, and deposit itself on the lens elements?