James Cole

Is there a difference in performance WITHOUT a tune? Any difference at all?

Thanks!

bonedaddyjr06

i never really noticed one without a tune

22kart22

well the only difference between kinds of gasses is octane rating, additive packages, and refining.

Since premium gas has a higher octane, it may give you a slightly better throttle response and power, but without a tune, the timing will be uncorrect. With a higher octane fuel, normally spark is retarded for optimal power..

viking396

Running higher Premiumin a stock GT isn't needed, if it's very hot our or you're going to the track using higher octane insures that the car doesn't have to pull back timing to insure no detonation/ping but for daily use, unless you tune it, no need.

Burnsy

is premium better for your engine - i know it will give some performance gains, but what about wear & tear on engine?

Drop Top 06

search search search.... octane rating has been discussed at least 3 times today on different threads... you'll notice quite a difference in the performance of your wallet if you have not tuned your car... you notice extra money disappearing for no reason... you won't see any performance improvements just by changing octane rating on a vehicle that's rated for 87

viking396

I'll say it again, premium is a waste if you haven't tuned for it. It has ZERO affect on wear and tear UNLESS you tune for 93 and put in 87. Buy the best you can afford and if it's stock put in 89 so you insure the computer doesn't HAVE TO pull back timing.

spdbrake

It is not that the higher octanes have more power, actually they are less volitale.
It really has to do with detonation resistance. The higher the number the less likely it is to pre-ignite, thus allowing two things.
You can run a higher compression engine. Be it NA or SC.
Can run a more advanced spark (Closer to TDC) in a stock compression.
The closer you get to TDC(more advance the more power)
A typical SC or NOS tune will have a retarded timing set. (ZEX wants stock only to a certain point, and then sometimes below stock timing.)
An 87 tune will have less WOT and Global advance than the 91 93 tunes for example.
Knock sensor: If you hear your engping for a short period during hill climb or accel you probably are experiencing detonation. the knock will tell the cpu to retard your timing, and you WILL loose some power. That being said the GT is said to run fine on 87, so you can waste your money on 91 or 93 but neither will harm your motor.
Now with tuners: The main diff in the three tunes you get is in the timing. "How far can it push it"
My car will not tolerate a 93 tune unless I run 100 race gas or run a 91 tune while using 93oct gas.
I can run the 93 tune all day (on 93)if I retard the timing 2-3 deg in the tuner.
Just remember detonation is B A D for your eng.
Probably better just to read this which can better explain it.
http://en.wikipedia.org/wiki/Octane_rating

06 gt

Absolutely 100% correct. Higher octane does nothing unless you have highcompression, or spark advance (ie. tune). Use of high octane in an engine that does not require it is just a waste of money. Gasoline companys do a great marketing job, making people think octaneequals quality and proformance. 93 octane in a stock Mustang GT ('05-'07) will give you 0 horsepower gain, 0 torque gain,0 speed gain, 0 gas milage gain. It will just cost youmoremoney than 87 octane.

tonkpils555666sas

+1... I put 87 in the car and it runs perfectly. I really dont notice much of a throttle response difference when putting 93 oct. If I tune the car to 93, then I can notice a difference, but it isnt that big of a deal. 87 is better... because gas is expensive as crap now!