silverbull271

If the 5.0 pushes 402 HP with 87 octane and 412 with 91 octane-------

Are there people out there who are actually going to alternate octane levels?

For me, once 87 always 87----once 91, always 91

I know its the worst thing to due to a car to switch back and forth, but Ford is kind of condoning it, no?

PS: Where does that leave 89 octane? somewhere in the middle of 402HP and 412HP?

Adam

I heard if you add 12 bottles of octane boost you'll break 500hp.

fritzOSU03

coffeejolts

I don't think there is anything wrong with switching fuel grades unless you have mods that require a certain octane. If you look at the label, I believe it say "minimum octane" or something like that. It isn't precise.

Lancel

Normal cars of old were designed for a specific octane of gas. Gas of an octane lower than the minimum recommended could result in damage to the car, due to the gas being too unstable for the engine, potentially resulting in premature detonations (knocking). Putting higher octane gas does very little to these engines, since they aren't going to take advantage of the higher octane fuel, so no performance advantage (my mom says the higher octane gas cleans headers or something, I don't know anything about that). There's also an air pressure element to this, as at higher altitude you can actually get away with a grade of gas lower (so in theory if it says 87 octane you can get away with 85 octane in the mountains, but once you get down from the mountains you'll likely get some knocking), but I digress.

Newer engines with the technology, such as the new Mustang engines, can advance the spark timing for lower octane gas on its own and has the capacity to detect knocking. As I understand it, this happens in the first few seconds of the engine starting, where it finds the point at which the engine starts knocking and then sets it to an appropriate level before that point. As far as I know, this is dynamic, and the manual makes no mention of any dangers in changing the gas in the tank, nor any special procedures, nor any warning of "Once 87 octane, always 87 octane". It should adjust itself in real time and continuously, so you can put in 93 octane with half a tank of 87 and it won't have any adverse effect, it will adapt based on if it detects knocking. Anything further and we get into mixture characteristics and how long it will take to fully burn it out of the system if you start mixing at half octane.

Now, will putting 100 octane gas in it make the 5.0 INSANELY AWESOME?! I have no idea honestly, but probably there reaches a point where the engine can't do much with it. Also, as mentioned, mods may potentially change things.

bpmurr

I've always run 93 in my cars. (91 in areas where it's not offered)

krnpimpsta

If you run 93 on an engine that does not have adaptive spark control, that was designed to run on 87, you will foul up your engine.

Higher octane generally means it burns slower / is less flammable. So if you are not tuned for 93 (or if your car does not automatically tune itself for 93), then 93 gas will not burn completely and leave residues in your engine.

krnpimpsta

that said.. i don't think there's any problem with running 93, 87, or switching between the two in a car that is designed to adapt to either one.