2 ways of measuring octane gains....points,and numbers.Points and numbers are very different things.One is just .xx,a gain of less than one whole number,and others are x. ...thats a whole number.So you could go from 87 to 87.2 or to 89.Normally the just a few buck additives will gain (if any) just a few tenths,whereas the old original 104+ or the first Outlaw (with MMT) might gain 4 whole numbers or so.In other words,if you need the octane,its cheaper to buy it at the pump rather than in a $10-20 bottle.Now if you have a 1968 musclecar with 10.5:1 compression...well,you need all the help you can get.