There is a myth that higher octane hurts cars AND THAT IS A LOAD OF CRAP!!! The fact is if it was harmful they would post it on the car as a warning or they would post it at the pump. The only reason not to run higher octane is that it is a waste of money PLAIN AND SIMPLE!!!
Now saying that if you live in a state like California
with crappy gas you might have to go to mid grade so the octane is at the required level. There are many people on the forums that have said they have had to use higher octane to prevent their car from knocking or pinging.