# Regular or Premium gas?



## CrazyGreek89 (Apr 2, 2007)

Whats the best for the gto, and what do you guys use?


----------



## Ninjured (Apr 28, 2006)

well, GM *recommends* premium and that's only what I use (preferably from a top teir gas station)

If you use regular, you might save $3 on the fill up but your goat will pull timing and you won't have as much power on tap. There is some octane sensor in your fuel system somewhere so it knows....


----------



## dustyminpin (Jun 19, 2006)

:agree 
Your goat will run fine as long as you haven't had a dyno tune or used a handheld programmer to advance the timing (like I did) otherwise your engine will spark knock itself into pieces. You won't have all 400 of your horses if you use anything less then premium, but the car should run without any engine problems.


----------



## koman (Sep 25, 2006)

Ninjured said:


> well, GM *recommends* premium and that's only what I use (preferably from a top teir gas station)
> 
> If you use regular, you might save $3 on the fill up but your goat will pull timing and you won't have as much power on tap. There is some octane sensor in your fuel system somewhere so it knows....


the knock sensor pulls the timing so you don't blow anything. i just use premium regardless. i'll par the extra 3 bucks and ride, you only live once.


----------



## Red Bearded Goat (Mar 19, 2007)

Basically, the manual advises using premium grade of 91 octane or better, lower grades can be used with a slight loss of performance. Knock may be detected using regular, yada, yada, bla, bla, bla.

I'd been using 93 for the 1st 2500 miles. My last fill-up I pumped in 3/4 tank of mid grade 89 as an experiment. My GTO ran great without a noticeable change in power or knock. Having consumed 1/2 this tank I'm looking at the avg. fuel economy display numbers appearing to be slightly lower so far while doing the same type of driving. I'm curious to see if the actual MPG decreased when I tank up at 1/4 with 93 again. I wouldn't consider using regular 87. That would produce engine knock sounding like a coconut telegraph sending out an SOS signal to feed it better Dino juice.


----------



## GTO JUDGE (May 14, 2005)

*My MPG on 1/2 a tank of 89 octane is no different than an entire tank of 92 octane. As a matter of fact.,... My best MPG which was just over 27mpg came with 1/2 a tank of 89 octane.*


----------



## Red Bearded Goat (Mar 19, 2007)

GTO judge said:


> *My MPG on 1/2 a tank of 89 octane is no different than an entire tank of 92 octane. As a matter of fact.,... My best MPG which was just over 27mpg came with 1/2 a tank of 89 octane.*


I can believe that on steady state driving at 65 MPH. I've had a mixed bag of driving on this tank. Stop and go city traffic, along with a few romps over 100 plus a few 20 mile interstate runs at 80 ... the read out shows 18.6 mpg and I expect that to be approximately 1 mpg off (high) from actual.


----------



## GTO JUDGE (May 14, 2005)

*Yea it was straight turnpike driving 65-70 on cruise. Normally I am in the 25 range straight driving no stopping.... Stop and go 19-21 ball park.*


----------



## fergyflyer (Apr 18, 2005)

If you drive 15,000 miles per year, that's the national average, and you average 20 mpg combined driving, we are talking about 750 gallons per year. At 20 cents per gallon difference in price that is $150 per year or $12.50 per month.

My thoughts are that we bought LS2 powered cars that operate at peak performance with premium gas. If you can't afford the extra $12.50 per month for the premium gas then you should have bought a car that was $750 less so you can really afford it. 

The LS1/LS2 runs best with premium. Pack a lunch twice a month or skip going out to dinner once a month and treat the car right so it lasts and performs the way it should. 

The difference between mid-grade and super is only $6.25 per week, so that makes even less sense to me.


----------



## GOATTEE (Nov 30, 2006)

fergyflyer said:


> If you drive 15,000 miles per year, that's the national average, and you average 20 mpg combined driving, we are talking about 750 gallons per year. At 20 cents per gallon difference in price that is $150 per year or $12.50 per month.
> 
> My thoughts are that we bought LS2 powered cars that operate at peak performance with premium gas. If you can't afford the extra $12.50 per month for the premium gas then you should have bought a car that was $750 less so you can really afford it.
> 
> ...



:cheers I couldn't have said it better myself. When I open my fuel cap it says on the inside "Premium unleaded ONLY" Oil changes cost a little more but hey if you want a high performance car do not cut corners.


----------



## PWR_SHIFT (Feb 10, 2005)

fergyflyer said:


> If you drive 15,000 miles per year, that's the national average, and you average 20 mpg combined driving, we are talking about 750 gallons per year. At 20 cents per gallon difference in price that is $150 per year or $12.50 per month.
> 
> My thoughts are that we bought LS2 powered cars that operate at peak performance with premium gas. If you can't afford the extra $12.50 per month for the premium gas then you should have bought a car that was $750 less so you can really afford it.
> 
> ...


True enough. Except for those living in colder climates, with off-summer ambients below 55 degs or so you can easily, WITHOUT ANY LOSS IN PERFORMANCE, drop down to 89, and even all the way down to 87 octane; the knock sensor will stay dormant. That's the effect of cold air my friends.

Otherwise, if you run lower octane in hotter ambients spark will be taken out, and if you insist on getting same level of pull out of your Goat, your mileage will suffer.


----------



## bigcountry (Mar 28, 2007)

Your'e driving a high performance car @ a high performance price, then put the high performance gas recommended, if i can afford the car then i can afford the gas:willy:


----------



## bigmac (Jul 9, 2006)

if IM taking a road trip with mostly highway driving I use 87 octane. I do not need the 'juice'. Normal city driving I use 91, occosionally 89. I do notice a significance power loss using 87 octane.!!!


----------



## bklyn77 (Apr 17, 2007)

Gotta pay the $$. My Diablo Predator Tuner REQUIRES premium gas via Mobil Citgo? Weird? 



dustyminpin said:


> :agree
> Your goat will run fine as long as you haven't had a dyno tune or used a handheld programmer to advance the timing (like I did) otherwise your engine will spark knock itself into pieces. You won't have all 400 of your horses if you use anything less then premium, but the car should run without any engine problems.


----------



## GTO JUDGE (May 14, 2005)

bklyn77 said:


> Gotta pay the $$. My Diablo Predator Tuner REQUIRES premium gas via Mobil Citgo? Weird?


*Requires either Mobil or Citgo? Sounds like an advertising ploy. Oh the power of advertising........

Your gas tank does not have the intellectual capacity to distinguish Sunoco from Citgo from Mobil to Shell.............

I will give NO MONEY to dictator Chavez. *


----------



## Confuc1ous (Feb 23, 2005)

The cold temperature thing is interesting, below 55 degrees, like in the northern part of the country in the holiday months of the year, if you drop down to 89, or even 87 octane, you get no engine knock and the car runs well on it? I am surprised.


----------



## EEZ GOAT (Jul 9, 2005)

my goat never tasted anything lower than 91. i did it to my grand prix gtp once and after i filled it up, it did not want to start. it took about 3 times for it to crank at the gas station and it ran awfull. never do it to your goat. its not worth it


----------



## GTO JUDGE (May 14, 2005)

Confuc1ous said:


> The cold temperature thing is interesting, below 55 degrees, like in the northern part of the country in the holiday months of the year, if you drop down to 89, or even 87 octane, you get no engine knock and the car runs well on it? I am surprised.


*
Although premium gas is recommended, 89 octane will not harm your engine. However I would not chance constantly using it. 87 octane will do harm. It is not worth the cost of an engine to chance using 87 octane. Just because you don't hear the knocking does not mean their is no damage being done.

If you search this thread you will see what I do my mixing 89 and 91 octane. I will alternate at 1/2 tank intervals if I see the price of 89 octane some 10-15 cents a gallon cheaper. I would not totally fill up on 89 octane. You may experience the car running well on 87 octane right now until one day when you notice something drastically wrong. The compression ratio needed to run this motor is being compromised. It's your car, but IMO you are starving the motor by using 87 octane. Your warranty will not help you should you have a claim.*


----------



## PWR_SHIFT (Feb 10, 2005)

Confuc1ous said:


> The cold temperature thing is interesting, below 55 degrees, like in the northern part of the country in the holiday months of the year, if you drop down to 89, or even 87 octane, you get no engine knock and the car runs well on it? I am surprised.


Don't be, air is denser when it's cold, and you have a knock sensor to adjust for the difference. I have a buddy who ran 87 octane in his LS1 Goat for three years w/out any issues, and when he occasionally gave it 93 during the summer he felt the difference, in the winter he felt none. 

Bottom line - No knock, no damage; don't let anyone tell you otherwise. The only thing a higher octane number buys you is knock protection . . . same as what the sensor does by adjusting engine parameters such as timing and spark.


----------



## PWR_SHIFT (Feb 10, 2005)

EEZ GOAT said:


> my goat never tasted anything lower than 91. i did it to my grand prix gtp once and after i filled it up, it did not want to start. it took about 3 times for it to crank at the gas station and it ran awfull. never do it to your goat. its not worth it


Your GP didn't have a knock sensor, did it?


----------



## Red Bearded Goat (Mar 19, 2007)

PWR_SHIFT said:


> Your GP didn't have a knock sensor, did it?


Yes, it does as do all modern computer controlled fuel injected engines. For the GTP, that be AC Delco part number 213-279. 

My 99 GP manual specifically states GTP's required 91 octane or better, but lesser grades could be used in an emergency. The L67 (code 1) 3.8 SC engine has a compression ratio of 9.6 compared to the 3.8 L47 (code k) in the GT having an 8.5 ratio (use the same knock sensor), both well below the 10.9 of the LS2 engine. 

The GTO manual suggests using 91 or better and says using a lower grade fuel will decrease performance. Not an apples to apples comparison or slam dunk but leaves room for owner interpretation. I'll post up a long winded rant on this later because I believe some people that posted on this thread don't know what the different grades of fuel are beyond cost and how they should effect performance because it cost's more money. In June I ran 89 with no ill effects except my MPG did go down.

Red.


----------



## GTO JUDGE (May 14, 2005)

*According to the manual... You can use 87 octane even though premium is recommended. If you ain't a knocking you'll be ok. I have seen some, not many with 85 octane. That is what I would avoid. That is the grade I refer to that can possibly cause damage. I personally won't use 87 octane as I stated previous. Some brands of 87 octane don't perform like other brands, and damage could occur, to me it just isn't worth the worry.*


----------



## GTO_Gregory (Aug 5, 2005)

The GTO will run on the High Octane fuel table in the computer until lots of knock is detected, then it shifts to the Low Octane table. There are lots of ways the electronics knocks down the timing. Piston slap and intake air temperature are two common knock-down tables. 

On a 2006 GTO the timing is reduced by one degree starting at 95 degrees of intake air temperature. This increases to ten degrees when the intake temperature goes up to 167 degrees. 

I live in Texas and on a 95 degree day outside the intake air temperature may be 135 degrees at a standstill. 

Premium fuel may buy you five degrees of timing.


----------

