petroleum based (lets leave synthetics out of this). Some oils and fluids will break down certain types of rubber and make the rubber swell as well. I'm a hydraulics Technician so these are issues I deal with on a daily basis. petroleum jelly works just fine on weatherstripping. the reason I said to use a small amt. was for cleanliness only. The difference in oils and fluids are in the additives and molecular weights. Zrevolver is correct to also suggest a silicone based lubricant.
