Once I used an octane booster product called 104. I seem to remember that it was one can per 20 gallons of gas. I used one can to 14 gallons which is what I had at the time. Had to use it cause I ran out of gas and drifted into a gas station (only one in the town) and all it had was regular. My car needed premium, so I filled with regular and then emptied a can of 104 in it. Stopped the pinging and ran very well.

Problem was that the can of 104 was like $5, worked out to be about 35 cents a gallon for the additive. Premium was only about 20 cents more than regular, but when you got to have it, you got to have it !

Actually I have noticed several of the service stations near me have dropped their premium octane levels. Where they used to sell 93 and 94 octane their are now selling 91 or 92. Not a big difference in octane but they are still charging the price of the higher octane gas. No surprise there.