All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
It is permissible for you to rub any part of your body (whether the limbs that should be washed when performing ablution or other parts of the body) with oil before ablution. However, it is a condition that this oil does not prevent water from reaching the skin of the parts that should be washed when performing ablution. Also, the person performing ablution should make sure that the water actually reaches the skin of those parts because with the presence of oil, it might be that water does not reach the skin easily.
Allaah Knows best.