I use regular in my 2.0L 2013 Kia Soul and it seems I burn gas quickly. I put gas when it really cool (temperature) and I do not drive crazy. I'm very conservative when it comes to driving. Also, I keep the ECO button on in my car all the time. I take it off and I get worse MPG. Should I go 91 and try it or just stay with regular? What do you guys use/suggest? The gas stations I use are Chevron, Shell, and 76. I typically use Chevron or Shell more, though.