# Must take premium gas?



## Ejjw18 (Sep 3, 2009)

Do our GTO's HAVE to take premium or would they run just fine on mid grade?Also, i know we don't buy muscle cars for fuel economy but what are you guys averaging on MPG?


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## HP11 (Apr 11, 2009)

I've never tried anything but premium as that is the factory recommendation. I average about 16-18 MPG depending how I drive but have been as high as 24.4 on the highway but that was during a test I conducted. Cruise control, no A/C, constant 70 mph in 30 mile loops. I'll likely never drive it under the test conditions again since I didn't buy it for it's fuel economy as you said.


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## Ejjw18 (Sep 3, 2009)

HP11 said:


> I've never tried anything but premium as that is the factory recommendation. I average about 16-18 MPG depending how I drive but have been as high as 24.4 on the highway but that was during a test I conducted. Cruise control, no A/C, constant 70 mph in 30 mile loops. I'll likely never drive it under the test conditions again since I didn't buy it for it's fuel economy as you said.


Yeah buying a muscle car and expecting amazing MPG is just stupid. I'm assuming that if i drive it like an *******(which i will the first couple weeks i have it lol) that i'll get about 13-14mpg and then 16-18 when i drive it normal.


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## HP11 (Apr 11, 2009)

Driving it hard was my other test. It was much less controlled and scientific but the mileage seemed to bottom out around 12.


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## Ejjw18 (Sep 3, 2009)

HP11 said:


> Driving it hard was my other test. It was much less controlled and scientific but the mileage seemed to bottom out around 12.


I'm gonna try not to drive it TOO hard. I dont wanna beat the **** outta this car. The only thing that pisses me off is that I'm gonna have to drive it in the winter .


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## GTO JUDGE (May 14, 2005)

You can get away with mid grade 89 octane. According to the manual you may experience some loss of power. If she ain't knockin you can get away with it. 

I have used a mixture of both 93 and 89. At half tank fill with the other. The best mpg I have ever experienced (28.7 mpg) was with a 50/50 mix of 89 and 93 octane. I have never used a straight tank of 89 octane and would not do so. I have not mixed both in a while because locally the price between the 2 is close enough (a few cents) well, why not have the premium. When I was mixing there was a 20-30 cent a gallon difference. 

If you really have to scrimp.... try alternating octanes at 1/2 and 3/4 tank fill ups.


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## HP11 (Apr 11, 2009)

In California, or at least the part where I live, we don't have the option of buying 93 octane. 91 is about as good as it gets except for speciality stations. Basically, your mix of 89 and 93 is going to roughly average out to 91 octane. I don't think I'd want to go any lower than that.


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## GOATTEE (Nov 30, 2006)

*Mr*

I would never go less then 91 octane. It will knock if you do. That is just the part of the cost of owning a high performance car. We have talked about this before and the price difference just is not worth the mid grade stuff.

If you drive 10,000 miles a year and average 18 mpg you will
use 555 gallons of gas. Out hear in CA it cost a extra .07 cents from 89 to 91.

Total extra cost per year $38.88.....Big deal.

A tire for this car cost over $200.00.

When you do the math it is crazy


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## GTO JUDGE (May 14, 2005)

GOATTEE said:


> I would never go less then 91 octane. *It will knock if you do.* That is just the part of the cost of owning a high performance car. We have talked about this before and the price difference just is not worth the mid grade stuff.
> 
> If you drive 10,000 miles a year and average 18 mpg you will
> use 555 gallons of gas. Out hear in CA it cost a extra .07 cents from 89 to 91.
> ...




That's not necessarily true. The anti-knock sensors adjust for it.

Gasoline Octane
*Use premium unleaded gasoline with a posted octane of
91 or higher for best performance. You may also use
middle grade or regular unleaded gasoline rated at
87 octane or higher, but your vehicle’s acceleration may
be slightly reduced.* *If the octane is less than 87, you
may get a heavy knocking noise when you drive. If this
occurs, use a gasoline rated at 87 octane or higher
as soon as possible. Otherwise, you might damage
your engine.*


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## HP11 (Apr 11, 2009)

GTO JUDGE said:


> That's not necessarily true. The anti-knock sensors adjust for it.


But it will run as if the timing has been backed off. Even if it doesn't knock, if the octane is low enough to bring the anti-knock sensors into play, performance will be affected which is basically what your insert says so why bother with the lower octane gas?


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## GTO JUDGE (May 14, 2005)

Hes talking 89 octane not 87 and lower.
The insert came from the manual. If using less than 89 was detrimental to the engine it would state so and the warning label on the refill door would read required instead of recommended. 
The engine should NOT knock at 89 octane and there should be no miss firing or the timing being retarded. 
Simple solution just use 91 and higher. For the difference in cost the car will run more efficient.


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## Poncho Dan (Jun 30, 2009)

93 octane FTMFW. Some ask if you can tell the difference between 91 and 93, and I would say yes - my mileage is slightly better and there's more power available in the very low R's.

I actually get offended when I pull up to a pump and see 91, especially since they're charging the same price as the guy down the street selling 93.


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## HP11 (Apr 11, 2009)

Poncho Dan said:


> 93 octane FTMFW.


If they sold it here I'd use it.


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## HP11 (Apr 11, 2009)

GTO JUDGE said:


> Hes talking 89 octane not 87 and lower.
> The insert came from the manual. If using less than 89 was detrimental to the engine it would state so and the warning label on the refill door would read required instead of recommended.
> The engine should NOT knock at 89 octane and there should be no miss firing or the timing being retarded.
> Simple solution just use 91 and higher. For the difference in cost the car will run more efficient.


I'm agree with the last sentence, use 91 or higher. On the other point, if the knock sensors have to make any adjustment to compensate for lower octane an/or prevent knocking, performance has to be diminished, to some extent, however slightly, since the engine management is basically doing the same thing we used to do manually with cars that had distiburors.


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## fergyflyer (Apr 18, 2005)

What we figured out is that the car will run just fine on lower octane. It will or may have reduced power. Reduced power will also show up as reduced performance and redudced fuel economy. 

Here's what you need to think about, is it worth the price. 

The national average for mileage driven per year is over 12,000 miles. At 12,000 at an average of 19 combined city highway you use 632 gallons. Locally here, the difference is .10 between each grade. 

You will theoretically save a bit over $10 per month for using regular and $5 per month using midgrade. if you are the average driver. 

The car will have a reduction in power and that will translate into lower fuel economy. If that reduction is 5% your mileage will drop to about 18 miles per gallon combined city highway. You will now need to buy 667 gallons of fuel. 

So look at this example. 632 gallons at 2.75 per gallon or premium is $1738 per year in fuel costs. 667 gallons at 2.55 per gallon is $1698 per year. Your total savings is $40 per year or less than $4 per month. 

That's a guess, but there will be some performance loss and some fuel economy loss with regular. Also it will be harder on your motor and your emmission system and cause those parts to need replacement sooner. 

Even if it is $10 per month, if you can't afford premium you probably shouldn't have bought the car.


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## Ejjw18 (Sep 3, 2009)

fergyflyer said:


> What we figured out is that the car will run just fine on lower octane. It will or may have reduced power. Reduced power will also show up as reduced performance and redudced fuel economy.
> 
> Here's what you need to think about, is it worth the price.
> 
> ...


No i can afford it, i just was just wondering. Lol i'm getting 14.5 MPG right now in my 6.0 though . I guess thats what i get for driving like an *******. I knew this would happen though. I've only had the car for 3 days so of course i'm gonna want to mess around with it.


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## jpalamar (Jul 22, 2008)

I just put premium in it. Your only talking $4 extra a tank and if that is going to break your budget I hate to say when something breaks yours screwed. These are great cars but the few thigns that will break aren't the cheapest.

I have 17.5 when I'm hard on the tank, 19.5 when I'm driving normal. Best ever was 26 all highway.


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## jpalamar (Jul 22, 2008)

Ejjw18 said:


> No i can afford it, i just was just wondering. Lol i'm getting 14.5 MPG right now in my 6.0 though . I guess thats what i get for driving like an *******. I knew this would happen though. I've only had the car for 3 days so of course i'm gonna want to mess around with it.


A4 also just sucks for gas. I'm assuming thats what you have based on 14s


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## FastFrank (Jun 12, 2009)

Ejjw18 said:


> No i can afford it, i just was just wondering. Lol i'm getting 14.5 MPG right now in my 6.0 though . I guess thats what i get for driving like an *******. I knew this would happen though. I've only had the car for 3 days so of course i'm gonna want to mess around with it.


Lol, I averaged about 13 mpg for the first month I owned my goat. And I also lost about 3/4 of the tread from my rear tires. After owning the car for almost four months, my average mileage is up to 19.9. I don't drive like I stole it any more, but I'm also not driving like grandpa either.

It may seem like it's a lot more expensive when your looking at that sign with the gas prices on it. But it really isn't much more when you do the math. Besides, I bought this car for it's performance. I'll be damned if I going to do anything to reduce that performance to save a couple bucks at the pump.


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## Ejjw18 (Sep 3, 2009)

jpalamar said:


> A4 also just sucks for gas. I'm assuming thats what you have based on 14s


yeah its a 2006 A4. my buddy has the 2004 A4 and he's getting in the 17's. I just wanna be between 16-17 and i'll be happy.


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## jpalamar (Jul 22, 2008)

Ejjw18 said:


> yeah its a 2006 A4. my buddy has the 2004 A4 and he's getting in the 17's. I just wanna be between 16-17 and i'll be happy.


My g/s 05 A4 averaged low to mid 16s and she drives very spiritedly. 14s means your running the crap out of it, driving in only the city, or need a tune up.


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## Ejjw18 (Sep 3, 2009)

jpalamar said:


> My g/s 05 A4 averaged low to mid 16s and she drives very spiritedly. 14s means your running the crap out of it, driving in only the city, or need a tune up.


Well yeah must of my driving is in the city. And like i said, this is my 3rd day having the car so I've been having some fun with it and getting up on the gas and stuff so of course my MPG isnt going to be great right now.


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## gto_rider (Aug 10, 2009)

the best i've done in the city is 19 and that was filling up at 3/4 of a tank. usually i get 17-18. on the highway the best i got was 21.5 with my cruise on about 80. only turning the air for a few minutes every half hour or so. the worst i got was 20.5 but that was goin 95 and 100. gotta love the ones that don't care if they get a ticket.


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## Ejjw18 (Sep 3, 2009)

I need to figure something out to do about this MPG guys, any suggestions? I mean all yesterday i was driving normal. Didnt really go above 2000rpm's more than a few times and am still getting like 14.2 MPG. I had a full tank when i left the house yesterday and drove only maybe 40 miles and when i got home had 3/4 a tank. I need to figure out how to get at least 16.


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## GTO JUDGE (May 14, 2005)

How are you figuring your mpg?
Are you resetting the trip when you fill up to begin your calculation?

I trust you know how to do the math manually?

When you gauged your latest mpg was it highway or stop and go?


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## fergyflyer (Apr 18, 2005)

Ejjw18 said:


> I need to figure something out to do about this MPG guys, any suggestions? I mean all yesterday i was driving normal. Didnt really go above 2000rpm's more than a few times and am still getting like 14.2 MPG. I had a full tank when i left the house yesterday and drove only maybe 40 miles and when i got home had 3/4 a tank. I need to figure out how to get at least 16.


Did you reset the mileage computer when you filled up or befeore you started checking it with driving easy? 

If you didn't the 14.2 isn't accurate for the current driving.

If you did reset it to zero and this an accurate reflection then you need to look at your driving patterns or see if your car is running properly. 

Did you stop and talk to someone and leave the car idling? If you did shut it off. Did you go through a drive through to get lunch, skip the drive through and go inside. 

Take a look at the air filter. Replace it if it's dirty. If you car has over 30,000 miles and you aren't sure if the fuel filter has been changed, change it. Those things will only have a minor impact on fuel economy, but a bunch of minor things help. 

Check the tire pressure. A lot of car dealers intentionally lower the tire pressure to make the car ride better. Keep it at 30 psi at least. 

If you've reset the trip computer for the fuel mileage and you've checked all those other things and you didn't idle a bunch etc.... then you will have to figure out how to live with 14.2 mpg or look for a different car. Tip here though, you will lose 2-3,000 trading in your car. That's enough money to buy 1000 gallons of gas and drive 14,200 miles for no money.


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## Ejjw18 (Sep 3, 2009)

fergyflyer said:


> Did you reset the mileage computer when you filled up or befeore you started checking it with driving easy?
> 
> If you didn't the 14.2 isn't accurate for the current driving.
> 
> ...


Well I just got the car 4 days ago so i'm not getting rid of it haha. Yes i reset it after i filled up. I have not checked the air pressure in the tires yet though. My friend has the 5.7 A4 and he's getting 18mpg so I don't see why I'm getting 4 MPG less than he is even though i do have the 6.0


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## rextheracer (Jul 3, 2008)

our cars are designed to run on premium. from what ive heard the octane of gas is the combustion point. the lower the octane the earlyer the combustion. if you put less than premium in the tank, the gas wont be ignited at the proper time, resulting in lower performance.

in another perspective putting high grade gas in a camry or something like that could also hurt performance because of the off timeing combustion rate.

to be honest, i wouldnt put anything other than what the gas lid says, plus like mentioned, the price difference in gas is really not that big of a deal. if you buy a goat, you have to take responsibility for the high costs in that kind of stuff..


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## gecko454 (Apr 25, 2011)

Historically, inflation adjusted gas prices are cheap, let her rip.


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## RKLamb (Jan 27, 2011)

Man I tried to run 87 yesterday without resetting my diablo tune lol. Man i had to get more gas about 50 miles later.


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## IcemanGTO (Mar 2, 2011)

I recommend only using 91+ octane gasoline in your 04-06 GTO 
because that is what these LSX engines are designed to run on.
Sure you could try running 89 octane mid grade and you will 
experience decreased performance,worse MPG,and very possibly 
detonation or knocking which isn't good for the LSX engines.
I don't think it is worth it seeing how much coin it is to rebuild 
a LSX engine think about it.
I will only run Chevron/Texaco premium 91 octane gasoline and 
my car runs excellent on this brand gasoline.
I highly recommend only using a high quality "top tier" gasoline like 
Chevron/Texaco brand gasoline.


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