Originally Posted by bill_de
89 is the optimal octane for the compression ratio, default timing, and whatever else the computer adjusts for. If you use 87 typically the timing would have to be retarded. The Jeep will do this automatically. You could loose a little pep racing from a stop sign and may get lower MPG. Depending on your driving habits it might not be enough that you would notice.
It will not hurt the engine.
On pre-computer controlled engines you would get a lot of pinging. The pinging indicates a problem that over time could cause damage. So love em or hate em, sometimes computers do good.
Good deal. I ask because the dealership told my my Z06 would throw a bunch of codes if I tried that and possibly need an ECU reset or some such because of how the fuel/timing tables would respond. Good to know that this is fine!
*As a side note, Ford lists the Mustang 5.0 as losing about 8-15bhp, IIRC, using low grade fuel, the ECU is fine with it, and re-maps the fuel/timing tables for it. So the loss should not be much for the JGC.
Most of my complaint is all the damn Ethanol. Where I'm moving, there is an E Free gas station! (In a town of 500 people...yay!)