Most octane boosters say in tiny print, that you need to add something like 1 bottle for every 1 point boost in 10 gallons. In other words, you need a lot to make a measurable difference. So you could get your octane up to par with maybe 6+ bottles and drive around to stir it up. But it is not cost effective and not necessary unless you drive like a maniac all the time.
The LS V8 runs fine, especially in cold weather with 87 octane although under hard acceleration you probably will get light to moderate pinging. If your engine is older, ie carboned up, or out of tune, it may knock more. Some will scream that your engine will explode. I have my doubts, but read the manual and come to your own conclusions.
If you are an enthusiastic driver, I would soft pedal it for now and add some 91+ as soon as the tank drops to say 3/4.
I run 89 most of the time and never detect ping. WIth 87 I get ping under hard acceleration or hot weather. With 91+ you are following the factory recommendation and are presumed safe, if your engine is in decent shape.
Side note, engines that are run gently at low speeds, say 55mph or less, tend to "carbon up" over a few months and will ping and run a bit sluggishly. You need to periodically wind it up a bit. I had a 79 TA that hated to commute, back in the "55 stay alive days", and needed to be stomped on every once in awhile to clean it out. Normal freeway speed RPMs was around 1500, so it really liked a good romp up past 4,000 once in awhile.
Good Luck,
Jim Henderson
