I've heard both stories, some people including my mechanic say that Super will give you better mileage and others say it burns away faster.
Some say that 87 is more wasteful since the fuel isn't as efficient as Super.

I wish we some solid proof and tests so we know who to believe.
I guess if you run the mid-grade 89 then your basses are covered.........hehe

keep in mind new engines are designed for certain octanes tho.
Old cars would benefit from 92, but using it in the Chally 5.7 might be worthless.