I don't think there really is a wrong answer. The engine will run fine on 87. I love that wording is something similiar to " for optimal performance run 89".......what the heck does that mean. if running 89 got you .001 mpg better you could say see you need to run 89 for "optimal" performance.
That being said I seem to run mine opposite of everyone else. If I know a tank of gas is gonna last me several days and I may be around town, in stop and go traffic or idling for a while, or going back to work and such which is normal for me I run 89. Just figure in the Texas heat anything that may help the engine I want.
However on long road trips where I know I am just going to be burning fuel, like hunting trips or family trips, where a tank or 2 a day is normal I just use 87 octane because the engine is just cruising down the road.
Again doubt there is a wrong answer just my $0.02
2016 Dodge Rebel
aka Project Black Sheep