Maraman

Bama told me you can run higher octane with the lower tune but not lower octane with the higher tune.

like use 93 with your 87 street tune, but you dont wanna run 87 with your 93 race tune.

brycerichert

This is VERY true.... You can always put in higher than you need, but you don't want detonation!

JIM5.0

Agreed. Although, if you are a penny pincher, putting in say 100octane when your tune tables are written for 93 octane at most, you are only wasting your money.

Basically, you don't need to put higher octane fuel than what you runs is written for. To take advantage of 100 octane fuel for example, you have to have a tune written for it.