I've been using Shell 93 Octane since i bought mine, i've used Chevron 93 a few times and i feel my car so different.
There is over 28,000 miles on my 11 ECO; all run on Mystery brand fuels-never Top Tier. The engine has always run excellent. IMO, just as the posts say, it’s all in your head-just a by the pants feeling, overpriced & does nothing different than the Mystery brands. And the MPGs’ my ECO actually gets- not DIC lies-very few postings with higher numbers.Its funny I felt the same way too lol. I filled up a few tank fulls of shell 93 octane and my car felt more "responsive or smoother" but when I switch to back to chervon my car still felt the same when I used shell 93 octane. I dunno maybe it was all my in head? lol either way both are good and our cars love it.