For those of you that have a stock 300hp GT, what Octane Grade are you using at the pumps? From what I heard, the GT can run on 87 (Regular). I'm just wondering if that's what most people run.

 

a 3-valve engine is really meant to run higher octane. but in the mustangs case, the new ford computer system, the spanish oak and all the knock sensors the mustang is equipped with, the engine can run regular which is recommended in the owner's manual....someone please tell me without having a tune, what could some of the possible benefits be of running a higher octane either 91 or 93

 

It's a waste of money to run anything higher than 87 octane if you don't have a tune.

 

I run 89 in my GT. It seems to run a bit better. Probably just my imagination and a waste of money. Only cost me a little over a buck when I gas up.

 

i agree with rich...total waste if u run higher octane without a tune...save ur money, even if its a dollar, stop padding the pockets of these oil companies if u dont have to. they r robbing us

 

I know but with the Flowmasters when I punch it ...It's the sound that makes OPEC stand up and cheer.

 

93 Octane with a Tune from Andre at CPT of Houston

 

I ran 89 octane on the stock tune here in Germany. The gas they sell on the military post is not quite 87 octane (something like 86.7-9). Running 89 octane was good insurance against detonation because sometimes you can get bad gas that has a lower octane rating. I never ran 93 octane on the stock tune because the tune just cannot take advantage of the higher octane rating. Running 93 octane on a stock tune is just pissing money away IMO.

 

Here in Holland the lowest grade is 95 (premium, equivalent to US 93 octane). I've used it before the tune too.
Once I did try 100 octane in Germany, but without a tune there was no noticeable difference.
Be wise and don't waste your money! If you can, use the lowest grade without a tune and the correct one when tuned.

 

I've been running 87, but I've been noticing a knock under heavy throttle...or something that sounds like one.

Switched to 89 on the last fillup to see if it's gonna make a difference. Haven't been able to tell yet.

 

I know we have had this discussion before and what it comes down to is you should only run what is recommended if you are running stock. Anything else, in time, will damage the engine.

 

You're not the only one! Same here. Certain gas stations' 87 seems to make the engine knock a little, while other stations it isn't as noticable. Temperture (warmer) seems to make it more prevailant too.

 

From what you heard??? Have you read the manual yet?

 

http://forums.bradbarnett.net/showthread.php?t=12168
Fuel topic Jan 05

1

 

My car "pinged" several times when running 87. I run 89 now.

 

89 is cheaper than 87 here so when it was stock I filled it up with 89 octane. Ran fine. Now have Brent's 93 tune so I have to use 93. Performance is

 

87 - no ping - still lights up the tires and makes me smile...

 

I run 87 with a brenspeed tune. Have plenty of power. I plan on going to the track soon and I will switch to 93 and change my tune a few days prior.

 

JOHN, you win the award for most avatar changes 87 for me

 

I have just over 5,000 miles on my car, all of them with 87. Runs great.