There has been a lot of negativity talked online about Arco and little discussion about the reviews and insights of Arco when they became TopTier in June of last year.
As some may know, Arco is now part of the TopTier list of quality gas in the US. They claim their gas is on par with strict standards exceeding the minimum requirements of detergents, same as with Shell, Chevron, etc. There are posters throughout the station stating TopTier. So I gave it a try, filling up with 91.

Filled up after a tank with Shell V-Power with Arco 91 and these are my findings:

1. 5 mins after start up, sitting at a red light, I felt the car have a quick/slight stumble, telling me the ECU was adjusting (in this case, retarding) the timing. Car idled normal afterwards.

2. My MPG dropped about 1-2. Comparing my normal city route, I used to get ~23mpg. I am now getting no more than 21 at best.

3. Decreased power. Definitely felt the car had more lag, throttle inputs felt so numb, car barely pulled at low rpm, mid range punch felt like a 4 banger, and the revs took noticeably longer to get to redline in every gear at WOT.

These findings were compared in very similar driving situations, driving characteristics, and environments with small deviations.

I thought all TopTier gasolines should be very similar in getting the expected performance and cleaning agents in them, but I don't think I'm going to use Arco again after my findings. I understand different brands have their own detergents, amount of ethanol, and that some gas comes from the same major refineries but I haven't had these symptoms using Chevron, Shell, 76, Costco, or Safeway.
Anyone who specifically used Arco when they became TopTier want to chime in or discuss their experience with them, post them here.