Mineral oil (or liquid petrolatum) is actually a by-product of oil distillation, and is sometimes injected for long-term sculpting purposes. Some people have experimented with injecting mineral oil in the same way as saline (temporary) or silicone (permanent) would be done. The results with mineral oil are usually permanent, but unpredictable, as well as having highly questionable medical safety. In addition, side effects have included cascading scarring. Mineral oil injection, while apparently plausible, is generally not recommended.
If you do this, you will probably need reconstructive surgery—we strongly urge you not to try this.
Article at Wikipedia