Most soft plastics have some type of scent
already "baked" in the plastic.

some guys used to swear by WD40.

First time I tried WD 40 caught some nice fish. I quit using it in fear the fish might grow a third eye or something freaky ! LOL

It worked anyhow.

Interesting posts. The actual science concerning scents seems rather limited.
So in that case I have to go with my own experiences. I believe at times scent did make a difference.
A few times I caught a big bedding bass by totally soaking the bait in crawfish attractant over and over- the surface had a film buildup- lol!- I think a few times it helped to trigger her to bite but I can't be sure. Also, I have been jig or worm fishing very very slowly for non spawning bass and noted an increase in big bass bites using attractant- esp crawfish, shad, or night crawler. Once again, can't be sure but it seemed to get more big bites. When you are sitting there forever waiting for something to hit your lure any little bit of confidence helps!

I know from my testing that insect repellant with DEET, sun screen SPF-50, grease, outboard oil, gasoline, and a few others I tested do not deter wild bass from taking a soft plastic lure. They may in a laboratory environment with trained bass.

I knew some old timer bass fishermen that would spit tobacco juice on their lures to get more bites. Same BS that some think WD-40 is made of fish oil and is an attractant.

Wayen, my Grand Father chewed Bull-Of-The-Woods Plug Tobacco. He would spit juice on my wad of worms when fishing for Catfish. We always seemed to catch the bigger fish when he did this.

Haven't heard any mention that WD-40 is made of fish oil; but it has been know to work.

We all have done test on our personal baits hoping to get better results. I have always had a hard time telling what works and what doesn't in our lakes because of the few bites that one gets in one day. I could have just got on some fish in that spot; who knows. I like testing these scents in Mexico where the catching can be up there around 100 Bass per day or more. Also half of those can easily be over 5 lb fish. We use counters to click each fish caught so it is quite accurate. Each trip I prepare 6 gallon bags of Brush Hogs and Lizards each containing a different scent. The boats that are fishing with Minnow, Night Crawler or Crayfish will always come in with more and bigger bass than the other boats. Those boats easily have 100 per day and the others run about 70 per day.
We fish 6 days; so by the 3 day no one wants to use the other bags...Go figure. Ha..

I think it's more of a cover for our scent I used garlic spray most of the time,even Pam cooking spray has worked for me

Ive read studies that say minus a chum bag, attractants do little to move fish towards a non moving bait. Once they take a lure, they quickly hold on or spit it out depending on texture or taste. Oil and gas don't bother them but deet does. I will spray mine occasionally not as an attractant but as a cover scent but can't tell that it actually helps. Plastics, I did the tail in a garlic flavored dye. I seem to catch more fish with it but who knows. I feel that it gives me a little longer to set the hook. I have confidence in that so I use it. It definitely doesn't seem to hurt and the tiny bottle lasts forever.

I believe the eyes and lateral lines play a more important role in the fish biting

WD 40

http://www.wd40company.com/files/pdf/msds-wd494716385.pdf

I saw the coffee flavored plastics a few weeks back in BassPro, and came up with the idea for a new plastic. I'm in the process of making it now...combining these two will be an absolutely killer lure! It may even be banned from most tournaments. I'm calling it "coffee black, cigarette" and you should use it right at sunrise for best results who knows, it may even mend your broken hearts

Grease and gasoline are not water soluble, so they would be undetectable to the taste receptors in a basses mouth. Deet on the other hand, is water soluble and is an extremely strong bass repellent. Again, I'll point you in the direction of peer reviewed repeatable scientific studies. In laboratory settings with bass that had never seen lures (let alone been trained) Keith Jones showed that strikes rates and hold time decreased dramatically for up to 45 minutes with lures exposed to deet. Again, this is published information by a biologist with a PhD. But by all means though if you did a backwoods study and want to douse your baits in insect/fish repellent go right on ahead! That'll leave more for me.

Fishermen are much like golfers in that if they think something will give them an edge, money is no object. Being both I've seen first hand how it works. Fishermen will buy every lure, scent, line, etc. available if they think it will help them catch fish. Golfers are notorious for buying drivers they think will help them hit the ball farther. With over 40 years of doing both, here is what really works. Fishermen, want to catch more and bigger bass? Hire a guide as a teacher and spend all the time possible on the water practicing what you learned. Golfers, want to learn to hit the ball farther and straighter? Hire an instructor and spend lots of time on the range practicing what you learned. KVD didn't win all those tournaments because he uses scent on his lures. Tiger Woods, forget that one, Jack Nicklaus didn't win 18 majors because of the driver he used. I credit my success as a fishermen to hiring Dreabon Joiner when I decided to get serious about bass fishing. The 14.19 I caught was a direct result of his teachings and time on the water. My success as a golfer came as a result of the lessons I got from various instructors and the many hours spent on the range.
If you want to spray something on your lures help yourself, but if there are no fish around it probably ain't gonna help. Just my 2 cents, spend it wisely.

I was on the bubble, but after this weekend on Choke I have to say that scents do make a difference.

I don't know that I get more bites with a scent, but I'm convinced that they help me catch more fish. With Megastrike on my lure, they don't spit it back out. If I don't feel the bite, I still can still catch them because they don't let go of it.