I used to use 2 cycle oil as well until i tried OptiLube. The 2 cycle creates ash as well as does not add cetane or have antigel properties. Until OptiLube i had used different brands of additives that didnt do much if anything. The 2 cycle oil did only 1 or 2 things and that is added lubricity which in turn made it run quieter. It did not add mpg which the OptiLube did. Just my 2cents.
2 cycle oil does seem to have some pretty decent anti gell properties. Take a look at the project farm video about it. I think it can as a big surprise to see it work. Can't really add it after it's gelled but works well before hand.
But as I said earlier. I've tried a few, don't remember them all but where off the shelf auto store stuff, and didn't see any difference in my truck. So I stopped spending money on them.
I feel that with a properly running engine with a healthy injection system, and not running poor quality fuel that additives will not do much if anything to help with noise or mpg. Engines with deposits or clogged nozzles, bad fuel, etc may see some improvements
I'd like to see a test on several low mileage vehicles driven the same course threw multiple tanks of fuel try out different additives and see if there is any noticeable difference. Then do the same with some high mileage ones.