Does that octanne booster gas treatment work? Options

[belizecelica]

I usually put high octane petrol in my tank and sometimes if im in autozone or walmart ill buy a bottle of octane booster and put it in my tank. I dont really notice a big difference, in fact none at all. A friend told me that its better to put it in at half tank to make it more concentrated. Does it make a difference? is it good for your engine???