Now you've gone and ruined all my fun...of which I had clearly implied I was having.
There are a lot of variables that the manual cannot predict including altitude, humidity, ambient temperature, engine temperature, all of which can significantly encourage detonation....
That is true
However, I'm sure chrysler engineers have taken all of that into consideration when manufacturing the 5.7.
Otherwise the manual would have stated: USE A GASOLINE WITH AN OCTANE RATING OF 89
instead of stating 87-89