Answer: Grease like Vaseline prevents water from touching the skin when its layered, caked on or dried. On the other hand if Vaseline isn’t dried it wont prevent water from touching the skin. While at the same time the hands, legs, or any other limb that must be washed during wudu should be thoroughly touched with water using the hand. If a person doesn’t use his hand to wash those limbs thoroughly, maybe the water will just slide down and off without touching the skin. This kind of grease: when dried can prevent water from touching the skin. When Vaseline is dried its like a layer of skin. Therefore the person using it should be aware and remove it before performing Wudu. And if this petroleum jelly isn’t dry then there’s no problem in making Wudu with it on the skin.
Fatawa Nur Al Darab tape # 229 side #2. http://www.ibnothaimeen.com/cgi-bin/art-noor/exec/search.cgi?cat=242&template=index%2FSound.html&start=401&perpage=100 Translated by Abu Aaliyah Abdullah ibn Dwight Battle. Doha, Qatar 1431