Why does the ford explorer sport only run on the premimum octance gas?

Answer 1

If your owner's manual recommends premium, it is only a recommendation. It will run on 87 octane as well. If the owner's manual says 87 is ok, and you are having a spark knock unless you run premium, then something is probably wrong. The manufacturer makes fuel recommendations based on PCM calibration(internal programming stradegy) that also affects the ignition timing of the engine. If your owner's manual says to run premium, that is why, but again, that is only a recommendation. It doesn't mean that it wont run on the other, or that there will be any engine damage because you ran 87 octane.