They sure advertise it enough. I used to use something called Tufoil and you could really feel a difference in response. I understand that it just may all contain silicone whicch can clog oil passages. Anyone? PB

 

I just found this:

http://www.epinions.com/content_2969477252

 

I used one of the types mentioned in the link. Once!
I don't think I will ever use any additive again. Strait oil is good enough, if your using good oil. Most are good, some are better. I can say, Quaker State will never see a dime of my money however. I used to work on cars and couldn't believe the crud build up in Quaker filled motors! On the plus side, I've never seen any motors as clean as the ones who have used Castrol in them. My Twenty-six year old truck included.

 

Lucas Oil makes an additive that I've used. Added 1/4 quart to my oil tank to keep eng. temps down. Bike seems to run 10-15 deg. cooler.