What's the best affordable scar removal cream?

I was in a bad car accident last year and I ended up skinning my head on the windshield, so I have a medium sized abrasion that I would really love to see either gone or to see diminish a bit. I just wanted to know what's the best and most affordable scar cream that has worked for you? Something you can find either in a drug store or something like Wal-mart. I know Merderma supposedly works well, and I've heard of something called Bio-Oil that I was going to look into, but I want to know what worked for you.

Thanks in advance.