oops low test in my Challenger R/T

How empty was the tank when you filled up on the low octane? If you had some 93 still in there, you could be close to 89 anyway.

I agree that the computer will pull timing and it will probably be ok but these motors don't tolerate overheating so add 93 as soon as you have some room in the tank and continue to drive gently. If you hear any ping at all, back off.