Low oil

I got distracted during my last oil change and only put in 4 qts when I should have put in 5.5 qts. I was short 1.5 qts. I then drove 150 highway miles before realizing mistake. What kind of damage, if any was done to the engine?

As long as you never saw the oil pressure light turn on, or the gauge bottom out if so equipped, you have not done any damage.

No damage, no problem…

It’s unlikely there was any damage. Top it off and don’t worry.