The manual says Premium which is at least 91 octane at the Sunoco station by me, but will using a 93 octane make the driving experience any more fun? Is it good/bad to use 93 octane on a 2012 civic si? How's the mpg on 93 vs 91? Also, any experience or thoughts on higher octane (94+)? I just can't seem to find any good responses on how this car performs or is affected by higher grade fuels vs 91 octane. Thanks in advance for any informal replies!