In April this year I had to get my gallbladder removed which was pretty major surgery. The surgery itself was keyhole which means I have quite a few little scars. The biggest one being just above my belly button. I was told after surgery when my scar was quite raised that using bio-oil would help to heal my scar and make my scar not as visible.
What I have been doing is drenching a cotton ear bud in the oil when I come out of the shower and rubbing it into my scars, the massaging part is really important as it assists in the breaking down of the scar tissue and increasing circulation to the area all of which help your scar heal faster. I was doing this every day for months. I have definitely found that my scar has faded significantly and is more smooth.
I bought this from a chemist for around $25 and can also be used for: stretch marks and acne scars and uneven skin tone.
Side note: If you do have a new scar it is best to start using bio oil straight away as it will work much more effective, so the sooner the better. (once the skin is no longer open-if that makes sense)