[tw0scoops123]

Does the higher octane fuel have a positive impact on your engine(besides performance). I know 87 octane has a better chance of pre-ignition due to it's more volatile state.

I'm looking for impact on longevity n such. Or does the difference in octane just mean how much the fuel can be condensed before it can combust on it's own and that's all(ie doesn't have any impact engine life)?

Just asking if I decide to switch from 87 to 93.

 

[Kyle F]

Octane rating is the gas's speed in burning. 93 does nto react as quickly as 87. Therefore you can run more timing and compression without detonation or deiseling.

It will really do nothing for you car in stock trim except cat you more and actually hurt your performance slightly, but you will have less of a chance of engine damage using timing, forced induction, shaving the heads, etc.

 

[xxxxxxxxVintageV8]

Octane

2006 GT Premium - always use 87 - never have a problem. Car starts, goes forward and backward, car stops.

 

[Brent05redfire]

I see moms in their big SUV's filling up with the highest octane at the pumps all the time. and that is because most people believe that it is a better grade of fuel.
simply put, it isn't any better than the lowest grade. high compression engines require a high octane for the reasons noted above by earlier posters. I ran 87 on my GT for quite a while and noticed a little bit of pinging under hard acceleration. now I use 89 octane and the pinging is gone.
93 and any high octane fuels shouldn't be viewed as power adders. just use the gas that is right for your motor and your wallet will thank you. save your money for that turbo or SC setup.

 

[tw0scoops123]

I see moms in their big SUV's filling up with the highest octane at the pumps all the time. and that is because most people believe that it is a better grade of fuel.
simply put, it isn't any better than the lowest grade. high compression engines require a high octane for the reasons noted above by earlier posters. I ran 87 on my GT for quite a while and noticed a little bit of pinging under hard acceleration. now I use 89 octane and the pinging is gone.
93 and any high octane fuels shouldn't be viewed as power adders. just use the gas that is right for your motor and your wallet will thank you. save your money for that turbo or SC setup.

I hear ya, I'm going to buy a C&L intake, so I'm wondering what would the best grade of fuel would be for me. EVery1 seems to go for 93 octane. That's fine but I don't plan on pinching every little HP out of my motor since I'm not taking it to the track(if that's why every1 uses 93, I'm not sure). I just want to use what would be good for my engine when I get this mod.

 

[Dea. R&E]

Now...If you are going to install a tune with that C&L, then the tune maker will specify which octane to use. Sometimes the cold air intake will make a re-tune neccessary. My XCAL 2, came with 2 tunes, an 89 octane and a 93 octane tune.
Others here will know more about this.

 

[tw0scoops123]

I've been using 87 for about 9k right now. Does it matter if you switch over after that long? Does the engine get "used to" 87, or is it all in the tune?

 

[Kyle F]

Its all int he Tune. An enginer dopesn't get used to a type of gas.

To my knowledge, there is no long term timing trim, but there is for fuel. Though octane rating has nothign to do with the amount of fuel in the combustion process.

 

[8850]

Here's a post I made over on the Corral: http://www.corral.net/forums/showthread.php?t=755380

Our engines do need 93 octane based on results of my tests on my new 06. .35 et improvement and 3.31 mph is quite an improvement.

 

[Brent05redfire]

I've been using 87 for about 9k right now. Does it matter if you switch over after that long? Does the engine get "used to" 87, or is it all in the tune?

the engine management system should adjust timing to eliminate most or all detonation.
it doesn't matter when you change octane ratings. you probably won't notice the effects until after 1 or 1-1/2 tanks later. but, the sooner you change the better if you suspect you need the higher octane.
but, you can keep on cruising with the 87, just be mindful of hard accelerations. listen for pinging.

 

[tw0scoops123]

the engine management system should adjust timing to eliminate most or all detonation.
it doesn't matter when you change octane ratings. you probably won't notice the effects until after 1 or 1-1/2 tanks later. but, the sooner you change the better if you suspect you need the higher octane.
but, you can keep on cruising with the 87, just be mindful of hard accelerations. listen for pinging.

You think a 89 tune would be good enough...i feel like 93 is racing fuel.

 

[GTNOS]

question for you guys running an aftermarket 91 or 93 tune: have you been gutsy enough to try 87 in your car when you have it tuned for 91 or 93??? anything happened? pinging?? anything??? i would never do it, just curious...:tongue

 

[thump_rrr]

Here's a post I made over on the Corral: http://www.corral.net/forums/showthread.php?t=755380

Our engines do need 93 octane based on results of my tests on my new 06. .35 et improvement and 3.31 mph is quite an improvement.

Either your driving is improving or the air or traction conditions are more favorable. You wouldn't see those types of improvements from fuel alone.

That's the equivalent of a 35hp gain

Tests should ideally be done back to back to be directly compared especially when traction and environmental conditions can change so rapidly.

Do you have the air temps and barometric pressures and relative humidity for both days?

We record hour by hour something like THIS on days we test.

We then use a calculator like THIS to give us the Density Altitude Calculations

To give you an idea HERE are some timeslips from one day at the track.

The left slip is stock intake and factory tune on 93 Octane fuel
The center slip is the C&L intake and 93 Octane tune on 93 Octane fuel
The Right slip is the same as the center except for a set of BFG Drag Radials. If you look at the slip you'll notice I crossed the line 0.2 sec below my dial in and 4 mph slower since I was heavy on the brakes during bracket eliminations.

My difference between running 93 Octane on the factory tune and 87 Octane on the factory tune was 0.05 seconds. which temperature change, a difference in traction or just shifting could have been the difference.

BTW I have made over 550 1/4 mile runs with my 05 last summer so I'm very confident my numbers are accurate.

Keep in mind that 1/10th improvement in 60' times is 2/10ths improvement at the other end of the track.

 

[8850]

Either your driving is improving or the air or traction conditions are more favorable. You wouldn't see those types of improvements from fuel alone.

That's the equivalent of a 35hp gain

Tests should ideally be done back to back to be directly compared especially when traction and environmental conditions can change so rapidly.

Do you have the air temps and barometric pressures and relative humidity for both days?

We record hour by hour something like THIS on days we test.

We then use a calculator like THIS to give us the Density Altitude Calculations

To give you an idea HERE are some timeslips from one day at the track.

The left slip is stock intake and factory tune on 93 Octane fuel
The center slip is the C&L intake and 93 Octane tune on 93 Octane fuel
The Right slip is the same as the center except for a set of BFG Drag Radials. If you look at the slip you'll notice I crossed the line 0.2 sec below my dial in and 4 mph slower since I was heavy on the brakes during bracket eliminations.

My difference between running 93 Octane on the factory tune and 87 Octane on the factory tune was 0.05 seconds. which temperature change, a difference in traction or just shifting could have been the difference.

BTW I have made over 550 1/4 mile runs with my 05 last summer so I'm very confident my numbers are accurate.

Keep in mind that 1/10th improvement in 60' times is 2/10ths improvement at the other end of the track.

The air stats were as follows according to Weather Underground: 2/3/06 - Barometer 29.98, temperature 51.8, humidity 76%. 2/5/06 - Barometer 30.02, temperature 68.0, humidity 52%. On 2/3 I had a north (head) wind of 10.4 mph and on 2/5 a South East (tail) wind of 11.5 mph. I do have a Skymaster that indicated a plus 10 +/- DA on 2/3 and -10 +/- on 2/5. That's not much difference. My readings may not have been read right before my runs however.

Maybe you can determine if that is the difference. 60' on 2/3 was 2.063 and on 2/5 2.011. Now as mentioned I did have ET Streets on the second day. The weight of the car had to be somewhat more on the second day as I had 1/2 tank verses something just under 1/4 on the first day. The ET Streets on that 16" wheel were slightly lighter however. I could tell that when changing them out but do not have weight differences.

I would really like to know why it ran better the next day if the fuel was not the reason.

 

[thump_rrr]

The air stats were as follows according to Weather Underground: 2/3/06 - Barometer 29.98, temperature 51.8, humidity 76%. 2/5/06 - Barometer 30.02, temperature 68.0, humidity 52%. On 2/3 I had a north (head) wind of 10.4 mph and on 2/5 a South East (tail) wind of 11.5 mph. I do have a Skymaster that indicated a plus 10 +/- DA on 2/3 and -10 +/- on 2/5. That's not much difference. My readings may not have been read right before my runs however.

Maybe you can determine if that is the difference. 60' on 2/3 was 2.063 and on 2/5 2.011. Now as mentioned I did have ET Streets on the second day. The weight of the car had to be somewhat more on the second day as I had 1/2 tank verses something just under 1/4 on the first day. The ET Streets on that 16" wheel were slightly lighter however. I could tell that when changing them out but do not have weight differences.

I would really like to know why it ran better the next day if the fuel was not the reason.

For 2/3/06 I get -386.5 feet
For 2/5/06 I get +646.4 feet

That's a difference of 1033ft in the wrong direction.
Your first day should have been faster as far as air data shows.

Now if you were using ET Streets on the second day with a 68 degree air temp your 60' times should be in the 1.60 range especially on 16" rims.
I'm getting 1.77 on 17" BFG Drag Radials

A 1/4 tank difference is only 3 gallons at roughly 6.5 lbs-gallon so say 20 lbs which is equal to 0.02sec

More time behind the wheel is necessary before such theories can be substantiated.

FYI a higher octane fuel burns slower, this prevents pre ignition which allows more timing advance to be dialed in.
The car companies have strict air standards and CAFE ratings to meet and if there was such a great difference with 93 octane that would mean that there was incomplete combustion using the 87 Octane fuel. If this was the case they wouldn't be meeting epa requirements and their fuel economy would have been very poor.

.

 

[rainman]

I've posted on this subject in another thread in the recent past. I can't say if my experience is typical or not. However, while I experienced no problems using 87 octane when my car was new, after I'd racked up 8 or 9 thousand miles, I started to hear some pinging on sudden throttle applications. Dealer said they couldn't do anything about it, and it was "normal". Using 93 premium cured it, but I wasn't totatally satisfied with that remedy. Since it didn't ping when new, I figured it was probably due to increased compression from carbon buildup.

****Warning**** testimony forthcoming

At the advise of a local mechanic, I ran some Amsoil PI through my fuel system. Mind you, I'm skeptical of the usefulness of all those bottles of fuel and oil additives that you see on the shelves of parts stores. I see most of this stuff as "snake oil". I could be wrong, but that's how most of this stuff strikes me. Anyway, despite my reluctance, I tried a half-bottle of Amsoil PI. While my intial attitude was negative, I had to admit I was wrong. While it didn't cure the problem entirely, after running one tank of gas with a half-bottle of Amsoil PI, the pinging has all but gone away. I still hear it on 89 octane on occasion, but it's so slight that I have to have the radio off and be listening for it to hear it at all. I'm going to run the other half-bottle through the gas on the next fill up to see if it causes the pinging to go away entirely.

So, from my experience, carbon buildup did cause a problem as far as using 87 octane, and a fuel additive, despite my reluctance to believe such a thing could work, seemingly helped in reducing this buildup, thus causing the pinging to go away.

I admit all of this is anectodal. Other variables could be at play here, such as the quality of available fuel. All I know is this:

Car when new: no pinging
Car after 8 or 9 thousand miles: pinging
Car after using additive: much less (but not zero) pinging

I'm still seeking total conclusion to this issue....

 

[8850]

For 2/3/06 I get -386.5 feet
For 2/5/06 I get +646.4 feet

That's a difference of 1033ft in the wrong direction.
Your first day should have been faster as far as air data shows.

Now if you were using ET Streets on the second day with a 68 degree air temp your 60' times should be in the 1.60 range especially on 16" rims.
I'm getting 1.77 on 17" BFG Drag Radials

A 1/4 tank difference is only 3 gallons at roughly 6.5 lbs-gallon so say 20 lbs which is equal to 0.02sec

More time behind the wheel is necessary before such theories can be substantiated.

FYI a higher octane fuel burns slower, this prevents pre ignition which allows more timing advance to be dialed in.
The car companies have strict air standards and CAFE ratings to meet and if there was such a great difference with 93 octane that would mean that there was incomplete combustion using the 87 Octane fuel. If this was the case they wouldn't be meeting epa requirements and their fuel economy would have been very poor.

.

I really don't think it is my driving. I torqued the engine approximately the same and nailed it on both occasions. I can't watch the tach but I do watch the car lean. With 60' times almost the same then doesn't it have to be hp difference. Were it the head wind then my 1/8 should not have been much effected but I ran an 8.844 @ 80.66 mph the first day and 8.631 @ 83.18 the second. Maybe the additional break in time rather than octane. I wish I knew but I really don't think it was my driving. Been racing automatics a long time. I have a 98 Camaro auto that runs 10s with well over 500 passes.

With this drive by wire I don't think this car will see 1.6s or even close without programming to eliminate and more mods. This is a stock engine with only an ASP underdrive pulley.

 

[thump_rrr]

I really don't think it is my driving. I torqued the engine approximately the same and nailed it on both occasions. I can't watch the tach but I do watch the car lean. With 60' times almost the same then doesn't it have to be hp difference. Were it the head wind then my 1/8 should not have been much effected but I ran an 8.844 @ 80.66 mph the first day and 8.631 @ 83.18 the second. Maybe the additional break in time rather than octane. I wish I knew but I really don't think it was my driving. Been racing automatics a long time. I have a 98 Camaro auto that runs 10s with well over 500 passes.

With this drive by wire I don't think this car will see 1.6s or even close without programming to eliminate and more mods. This is a stock engine with only an ASP underdrive pulley.

I was unaware that the car had an auto trans.
That's completely outside my field of expertise.
It's kinda hard to launch at 5,000rpm with a stock trans.

 

[8850]

I was unaware that the car had an auto trans.
That's completely outside my field of expertise.
It's kinda hard to launch at 5,000rpm with a stock trans.

Sorry but yes it's an auto.

I checked out your web site. I like those headers. I bet they were a challenge to install. Good looking time slip too!

How much did the CAI improve your times? I tried pulliing my filter completely out but my times were within .003 seconds. Of course this was without tuning. The factory box has good size passages so I wouldn't think it is a restriction.

 

[thump_rrr]

Sorry but yes it's an auto.

I checked out your web site. I like those headers. I bet they were a challenge to install. Good looking time slip too!

How much did the CAI improve your times? I tried pulliing my filter completely out but my times were within .003 seconds. Of course this was without tuning. The factory box has good size passages so I wouldn't think it is a restriction.

Thanks

The headers weren't really that bad. It took about 7 hours in total all alone.

I got an improvement of nearly 3/10ths out of the C&L intake Diablosport combo.

A CAI and tuner would definitely be my first mod if I were you.

The SCT X-Cal II is the way to go with an automatic transmission from what everyone says. There are more transmission setup options on it.

You already have the pulleys so then I'd go exhaust and then gears.

For an auto I'd go 3.73 or 4.10 if you wanted to go more extreme

all the best with the new stang.