Related to the other thread about getting old caked on grease off of bearings, I'm now wondering what is safe/best to use to clean the same caked on grease off the rubber seals in the headset (or any other rubber pieces on the bike)? I've been reading that the mineral spirits I used on the bearings may not be ideal for the rubber and may cause issues. The citrus degreaser I'm using doesn't specifically list 'rubber' in its list of things not to use it on, but it's also not included in the list of things it is 'good' for.

Any suggestions?