This may be a bit off-topic but when I lived in Seattle and did a considerable amount of salmon fishing there were some guys who swore by an unusual fish attractant, WD-40. As I understand it WD-40 has 2 major ingredients, fish oil and kerosene along with some other top-secret stuff, I'm sure.
The fish oil is easy enough to believe since herring is one of the old standbys of salmon fishing. But I always wondered why the kerosene didn't just nullify any benefit the fish oil might bring. As was mentioned before, maybe the fish can't smell it or what I thought for some time was that it dispersed in the water much quicker than the oil thereby leaving only the fish oil on the bait after a short time. I don't know, but it's something that I've wondered about ever since I found out people used it.
BTW, I tried it but never really thought it made a difference either way.
Also, this was many years ago, I now know what a bad idea it is to put any petroleum product into a body of water.