[Ateup]

The guy I bought mine from used premium so I have been too. Is there any harm in doing so? Any benefits? The owner's manual said it was designed for regular and using premium isn't recommended. Just wanted some opinions. Thanks in advance.

[Winters98GT]

Your car is designed to run on 87. You will not benefit, and probably see a decrease in performance if you up to 91-93 octane. Unless you have a timing adjuster, or a custom tune with more timing, stick with 87.

[ThePumpkin]

welp. I dont have a 2v 4.6.... but I do run premium from BP.
When I first bought the car, I ran 87, then switched to 93. I noticed a slight difference in performance (maybe it was just mental) but it sure did feel like an increase in throttle response.. So i've run 93 since.
I would imagine that the owners manual says no premium because of the low compression, its not needed unless your running some form of forced induction or a stroker kit...
The difference between "regular" and premium is probably not going to effect your car THAT much as long as its unleaded. ... Thats another story, race gas will foul your 02s in a heartbeat.
Although,
Im interested in seeing what have to say about this... i've often wondered in the past if im wasting my money on 93

[Winters98GT]

Originally Posted by ThePumpkin

Im interested in seeing what have to say about this... i've often wondered in the past if im wasting my money on 93

yes, your are wasting your money.

[ThePumpkin]

Originally Posted by Winters98GT

Your car is designed to run on 87. You will not benefit, and probably see a decrease in performance if you up to 91-93 octane. Unless you have a timing adjuster, or a custom tune with more timing, stick with 87.

Theres the answer. I did notice a HUGE increase in power from a 93 octane tune.
A good tune will work wonders for any car.
But i still swear i noticed a little increase in performance when i was 95% stock... I guess it was just mental

[Winters98GT]

Originally Posted by ThePumpkin

Theres the answer. I did notice a HUGE increase in power from a 93 octane tune.
A good tune will work wonders for any car.
But i still swear i noticed a little increase in performance when i was 95% stock... I guess it was just mental

I would make sure that the car does not have any aftermarket tune on it, first. Detonation can due damage to a motor. If you run 87 and don't hear any detonation, or pinging, you probably have a stock tune and should keep the 87 in the car until you get a custom tune.

[ThePumpkin]

Originally Posted by Winters98GT

I would make sure that the car does not have any aftermarket tune on it, first. Detonation can due damage to a motor. If you run 87 and don't hear any detonation, or pinging, you probably have a stock tune and should keep the 87 in the car until you get a custom tune.

I have a custom tune... and oh wait... a 66mm turbo. haha forgot about that.
I was just refering to when I was mostly stock.

[Winters98GT]

Originally Posted by ThePumpkin

I have a custom tune... and oh wait... a 66mm turbo. haha forgot about that.
I was just refering to when I was mostly stock.

Since that is the case, I wouldn't be putting any Mom/Pop Gas in your car. Use the best, Chevron with Techron or Shell. No need to blow a motor over a bad tank of gas. You should know that owning a FI car!

[VEE EIGHT]

To the OP, only run premium if you've adjusted your timing or have a high-octane tune. I know that you have neither so you're just wasting your money.

[95.0Stang]

I went on a road trip...a 6 hour drive. I always use 91 octane and this would be no different. The first leg of the trip from Topeka to STL I got 27mpg, pretty good for a V8 car right? Then I filled up at a Mobil station in STL with 93 octane, really this was just to do it, I didnt expect any gains at all, but from STL to Indianapolis I got 30.2mpg which shocked the heck out of me! As I was leaving Indy I filled up with 92 octane which is the highest I could find around my hotel, and from Indy to STL I got 28mpg. Stopped at the same Mobil station in STL and filled up with 93 again, and the car did 30.1mpg back home to Topeka. This is MY experience, and why I just always use premium. I am sure there are variables, but honestly I thought these results were really great considering how my car is equiped. Ford said 26mpg HWY on the new car stcker for this car, so to beat that is impressive to me.
Current mods that COULD effect MPG...
1. O/R H-Pipe
2. Magnaflow Catback
3. Eibach Lowering springs( I figure aerodynamics may change and help)

Mods that SHOULD lower MPG
1. Heavier aftermarket Bullitt wheels
2. Heavier BFG tires in front
3. Heavier Goodyears to fit the 17x10.5 wheel in the back
4. Over 100 pounds of luggage in the trunk

Again this is purely my experience, and not based in science at all, just an FYI type thing!

[Pearl02]

Originally Posted by Ateup

The guy I bought mine from used premium so I have been too. Is there any harm in doing so? Any benefits? The owner's manual said it was designed for regular and using premium isn't recommended. Just wanted some opinions. Thanks in advance.

Like everyone else said don't run premium fuel in your car unless it's tune to do so. I work for a gas pipeline company. Our lab runs test for the quality control of all the products we handle. They use what we car a "knock" engine for octane testing. It's just a one cylinder engine bolted to a concrete base. The lab techs are able to advance and retard timing on the fly. Permuim fuel burns at a slower rate than unleaded. More timing can be added for improved power and torque. The testing takes awhile to complete. This is how we determine octane ratings for gas. It's been about 15yrs since I've seen this test run but it hasn't changed. What I have seen is if premuim fuel is ran with not enough timing carbon build up can happen. That can lead to pre ignition which can cause some problems down the road. Pearl02.

[Kilgore Trout]

Use top tier fuel and use an octane that is appropriate for your mods and tune.

I always run Shell 93 octane and I never let it get below 1/4 tank but I have a FI 4V.

When I had my old 2001 GT I would use Shell 87 but I would occasionally run higher octanes of Shell gas.

Top Tier Gasoline

[98COBRA281]

i run 93, because of my tune/compression



so shell is a pretty good gas? i used mobil for a while, but it sucks, lots of corbon deposites, in my and my dads motor, we pulled my dads heads off a few years ago, and the exhaust ports were filled with a thick coat of carbon

[SteedaGT9150]

Originally Posted by 98COBRA281

i run 93, because of my tune/compression



so shell is a pretty good gas? i used mobil for a while, but it sucks, lots of corbon deposites, in my and my dads motor, we pulled my dads heads off a few years ago, and the exhaust ports were filled with a thick coat of carbon

i always try and use shell or bp. im not a big fan of anything else, too many horror stories

[stangGT97]

When I fill my car up with Shell 87octane in Massachusetts, it runs fantastic. When I get back to NY and have to use gas from ANY station out here, it runs worse. I'm not impressed by the quality of Mobil gasolines, but where I am, my only choices are Hess, Mobil, Sunoco or Stewart's Shops gas, and Mobil is the least awful but still pretty bad.

Long story short, use 87 on a bone stock GT.

[tank_567]

I have two tunes, 89 and 93, i saw a 4rwhp difference between the two. I've been running 89 in my car and have been seeing 280-300 to a tank, about the same mpg on the 93 tune.

[patman0911]

I run 93 now because i cranked up my base timing with a timing adjuster. I ran 89 before the T/A because I thought I was feeling slight hesitation and pinging with 87, probably due to the 150 degree air and 500% humidity we have down here - oxygen molecules are far and few between in the summer.

As stated 50 times in this thread already, use 87 unless you've got a real reason not too - pinging or hesitation, or increased timing.

For what it's worth, I like Chevron with Techron. My car always seems happier when I fill up at the Chevron station but that may just be my imagination. In reality, I think any of the major brands are probably fine.

[oxfordgt]

This is a simple question to answer. If your not tuned for it then don't run it. Running 93 octane in a car tuned for 87 will cause carbon build up in the combustion chamber. Higher octane fuel burns slower which means that on a stock timing tune you will not burn all of the gas. This is what causes carbon build up and a loss i power.

[02LaserRed2V]

93 and 110 here

on a bone stock 2V, 87 will be fine.

[302GTS]

As said previously in this thread, it's an absolute waste of money, unless you're running higher timing (like the 5.0 guys!), or you have a tune for anything more than 87 octane. Our cars come from Ford built to run 87, that's why the 5.0's came with 10* BTDC timing, which can be bumped up if you choose to run a higher octane fuel.

[40oz]

I use premium most of the time. I see a real, measurable benefit on longer drives, but it is not substantial enough to see in daily driving around town.

Here is a link to an article that discusses this very topic, and some of you might want to read it before making assumptions:
Regular or Premium? - Feature - Auto Reviews - Car and Driver

FWIW, the original article featured a pic of the vehicles in the test, and the Mustang was a GT, not a Cobra, IIRC. It is my understanding that the 2001 Cobra requires premium, and uses a knock sensor, while the GT calls for 87 and has no knock sensor (even if they think it does in the article). We know it's a GT because they don't say it requires premium, and it's an auto.

Anyway, my own experience jives with the article. I'm not arguing running premium is cost effective, but neither is driving a Mustang GT in the first place. But I would suggest those who claim there is no benefit or even a detriment should really consider the evidence and do their own experiments. Just saying there is no benefit based on faith alone is kind of silly.

[Ateup]

Thanks again guys, good info to know.

[crazystang25]

Originally Posted by 95.0Stang

I went on a road trip...a 6 hour drive. I always use 91 octane and this would be no different. The first leg of the trip from Topeka to STL I got 27mpg, pretty good for a V8 car right? Then I filled up at a Mobil station in STL with 93 octane, really this was just to do it, I didnt expect any gains at all, but from STL to Indianapolis I got 30.2mpg which shocked the heck out of me! As I was leaving Indy I filled up with 92 octane which is the highest I could find around my hotel, and from Indy to STL I got 28mpg. Stopped at the same Mobil station in STL and filled up with 93 again, and the car did 30.1mpg back home to Topeka. This is MY experience, and why I just always use premium. I am sure there are variables, but honestly I thought these results were really great considering how my car is equiped. Ford said 26mpg HWY on the new car stcker for this car, so to beat that is impressive to me.
Current mods that COULD effect MPG...
1. O/R H-Pipe
2. Magnaflow Catback
3. Eibach Lowering springs( I figure aerodynamics may change and help)

Mods that SHOULD lower MPG
1. Heavier aftermarket Bullitt wheels
2. Heavier BFG tires in front
3. Heavier Goodyears to fit the 17x10.5 wheel in the back
4. Over 100 pounds of luggage in the trunk

Again this is purely my experience, and not based in science at all, just an FYI type thing!

well when your cruising or on a road trip your in closed loop 99.9% of the time so the compy is constantly adjusting the timing to get the best fuel economy and power at the same time, so with the higher octane it can advance the timing farther and allow the better mileage.

[crazystang25]

me with 3.70's in the rear can still pull down about 260+ miles per tank driving in town with premium.

[crazystang25]

Originally Posted by oxfordgt

This is a simple question to answer. If your not tuned for it then don't run it. Running 93 octane in a car tuned for 87 will cause carbon build up in the combustion chamber. Higher octane fuel burns slower which means that on a stock timing tune you will not burn all of the gas. This is what causes carbon build up and a loss i power.

again think about closed loop. computer will advance the timing to the point of detonation. then pull it back a degree or 2. of course open loop higher octane will not benefit you unless you are tuned for it.