138 in an Acura TL (2008)
I was with my dad and I had just gotten my permit a few weeks prior.
He said to me to go as fast as I wanted (in my comfort zone) to "get it out of my system". He wanted to make sure I'd go fast with him in the car, not alone and be stupid

We were on the open road (Back road through the mountains) and I was going 80, I thought that was fast.
I sped up to 90, before I knew it I was over 130 and could barely control the car after hitting some minor bumps in the road.
After hit my max speed of 138, I finally slowed down, didn't go faster than 80 the rest of the way there.
It was smart of him to have me go fast with him, instead of alone and being stupid.
Never again will I go that fast on an open road.
But I loved it

TL;dr: 138 and never again xD