MidnightGT02

Is running 93 octane on a stock 4.6L engine going to harm it?? I've heard that running higher than 87 octane on a stock engine somehow harms it...which im not sure how, but anyways...good or bad?

GT1999

what ??, is your poll debating wether to run 93 or 91? im not even sure how to make sense of that. you even said in your past that over 87 is bad... so why wouldnt u make the poll consist of an 87 octane option... oh well i say neither 93 or 91 ... use 87 . 91 or 93 if you up your timing would be cool , otherwise use 87... or if u really want to waist money use 89, but dont useanythign in the 90s

94Cbra

All octane rating is, is a fuels resistance to combustion. The higher the rating, the more resistant. You want to run the lowest octane you can without detonation. If your run to high of an octane all your gonna do is lose power. Use the lowest octane you can without detonating.

Vizaracer

my manual also says to run 93 octance fuel. also my gauges say premium unleaded fuel only so that means 93 octane i guess also?

Phillyblunt474

Go with the manual unless you have likea blower that requires 93 octane or something of the sort

Vizaracer

i dont have a blower and it says 93 octane though. [sm=smiley13.gif]

GT1999

thats wierd... just up your timing and then you can fill up 93 all day long and not worry about it

Soaring

The computer senses which octane you are running and adjusts accordingly. My Mach uses 93 as recommended by the manual.

SilverGTV8

My manual says 87, I have run 91+ in the car since it 5th tank. The car pinged on 87 and 89 gave it a weird flat spot in the RPM band. I run 91+ and it's fine. I tried switching back last fall and it did the same thing.

Now with all my mods I should be running 91+ anyways.

Higher octane = more controled SLOWER burn and less prone to pre-ignition. If the car isn't capable of burning it all, the unburnt gas will exit the exhaust system and if you have cats you will damage them.

Monch

for you guys with gt's asking for premium octane, are you the original owner? if so, where did you buy the car at? I'm wondering if location has anything to do with it. does ford ask for premium in cars sold in, say, arizona, where it gets hot, or something?