In the 10th civic hatchback (sport trim), the 91 is recommended, probably cuz it got a little extra horsepower I guess, up to 180hp rather than the regular 174hp
for the 11th civic tho, the power is also up to 180hp for sedan right with exhaust vtec added, and I believe it recommends regular
I use Shell 87 pretty much 95% of the time, mostly because their station is convenient to me. It's usually 10-20 cents higher than the cheapest stations but Top Tier. Premium (93 octane) is over a dollar more per gallon where I'm at (at Shell) so I'll stick with 87. Shell's 93 octane is good stuff though if you got the bucks.