I noticed something about using different fuels, do you notice the same?

[03ghoststang]

Your "study" was hardly scientific and your "results" are anecdotal at best.

Anyway, for the stock tune best to use 87.

In any case, use the lowest octane your can use without getting detonation.

pretty much but on a good percentage of mustangs they detonate with 87, so 89 will be the one to use but like stated before if you are using a tune that requires 91 or higher then that what has to in

 

[fox1x]

I guess that's the 'Ford Mystery'.. When I had my F-150, people at F-150online.com would always be rejoicing or complaing because exact same set-ups of some truck would be faster/slower than someone else's with no mods. Maybe the Mustangs are the same, ocaasionally some ping with 87 and need 89 or higher.

I never had the pinging, I just decieded to try 89. It just *seemed* to have better throttle response. Like I said though, the placebo is a powerful thing.

 

[jimfitzgerald]

That might sound good, but it makes no sense. Once the spark fires, it all burns. Octane rating only means it takes a higher pressure to ignite without a spark. It doesn't mean they added dirt and water to make it burn poorly :/ Higher octane gas might indeed have less energy per liter than say, 87, but the difference is so minimal you could make it up by cleaning out your glove compartment. A bigger issue concerning energy density would be oxygenated fuels used in the winter in most cities. Oxygenated fuel has less energy than non-oxygenated fuels, per liter, and you will get noticeably worse mileage.

AFAIK, the flash point of a fuel is unrelated to the amount of energy it stores. And octane has nothing to do with the speed at which the flame front propogates.

All gasonline isn't the same once you include additives, so one brand's 87 might knock, while another brand's doesn't. Every station in an area might get their gas from the same refinery, but use different additives to get the octane numbers they sell.

Sorry, but you are wrong. There is enough difference that it will affect your 1/4 mile times and dyno numbers. You should run the lowest octane called for by the manufacture unless you are getting detonation or have upped your timing.

 

[03ghoststang]

Sorry, but you are wrong. There is enough difference that it will affect your 1/4 mile times and dyno numbers. You should run the lowest octane called for by the manufacture unless you are getting detonation or have upped your timing.

you make a god point there jim, octane made a difference in my friends 91' camaro when he ran in the track in AZ since the track is open 4 times a week we tried different octane and he ran better with 89 than 91

 

[mrvax]

Sorry, but you are wrong. There is enough difference that it will affect your 1/4 mile times and dyno numbers. You should run the lowest octane called for by the manufacture unless you are getting detonation or have upped your timing.

This is correct. Unfortunatly for me, I do have to use 93. I have advanced my timing and headswaped into ~ 10.5:1 C/r.

 

[jimfitzgerald]

This is correct. Unfortunatly for me, I do have to use 93. I have advanced my timing and headswaped into ~ 10.5:1 C/r.

With my tunes, I run 93 on the street and 116 at the track.

 

[AmBo]

Excuse the RETARDED question, but what exactly IS detonating?

 

[jimfitzgerald]

Excuse the RETARDED question, but what exactly IS detonating?

Premature explosion of fuel in the cylinder. It sounds like marbles rattling around in a can. It can cause severe damage to your engine.

 

[03ghoststang]

Excuse the RETARDED question, but what exactly IS detonating?

it's not retarded you just didn't know what it was but jim just answered it for you and when that happens you go to a higher octane and see if it went away

 

[reddrgn01gt]

BP gas is crap. I've been told by my Ford dealership to steer clear of the big green...

After tuning my car I've had to use 91+ octane. It "seems" that my car runs better on Shell & Sunoco, but I think it's all in my head...

Bp uses amoco fuels. I use the 93 all the time with my predator and have never had an issue. In fact diablosport recommends that you use amoco fuels or another quality brand on their web site. So i would have to disagree with them saying it sucks.

 

[dustang50]

Bp uses amoco fuels. I use the 93 all the time with my predator and have never had an issue. In fact diablosport recommends that you use amoco fuels or another quality brand on their web site. So i would have to disagree with them saying it sucks.

They said it had to do with the ethanol, and that it would burn out certain sensors if used too much. I dunno. I'm no chemist, so I didn't question them.

Of course this comes from the same people who replaced my fuel pump with the wrong one... TWICE. Needless to say I don't take my car there anymore.

 

[mogs01gt]

I only run 94 octane, that is what it was tuned for.

 

[WillDuhhBeast]

BP gas is crap. I've been told by my Ford dealership to steer clear of the big green...

After tuning my car I've had to use 91+ octane. It "seems" that my car runs better on Shell & Sunoco, but I think it's all in my head...

Agree'd on shell gas.


I've tried lots of gas around in this area.. and gate and chevron seemed to act the poorest.. although it could have been plenty of things, probably the weather.

 

[40oz]

Sorry, but you are wrong. There is enough difference that it will affect your 1/4 mile times and dyno numbers. You should run the lowest octane called for by the manufacture unless you are getting detonation or have upped your timing.

I got my info from this faq:
http://www.faqs.org/faqs/autos/gasoline-faq/part3/

It lays it out pretty clearly, if a bit on the technical side. It makes no mention of the drawbacks, other than financial, of running too high an octane. And it depends on what is used as an additive to achieve the octane rating.

If ethanol or methanol is used to raise gasoline octane, it will lower the energy density of the fuel, and winter oxygenated fuels are noticeably less dense, as is ethanol-containing gas. That said, use whatever works. I'm certainly not going to argue with anyone who found lower octane works better for their needs. But the suggestion that higher octane doesn't burn as well in an engine is inaccurate, according to the link. I don't doubt the fact that one grade/brand might perform better than another in a particular car, though.