Just wanted to add that I didn't mean any disrespect with the "my car ran smoother" answer.

I few months back I read a report about a university study sponsored by a government agency (don't remember which one). The results were as stated above. They used the results of the study to go after the companies regarding their claims in advertising. Some had to change their advertising, some paid fines and some can no longer be found on the shelves.

I also feel that if Toyota felt they were necessary they would be stocked and sold at the dealership. These are the same people who try to sell you "baby spit-up protectant coating".