After I filled up this morning I saw that I had put in 13.5 gallons. My manual says my 2007 N/A has a 13.6 gallon tank. I can't believe I was that close to running out. Last range estimate I saw on the DIC said 44 miles (I leave it on all the time because the analog fuel guage and low fuel warning light are pretty useless). I know I only went 30 miles after that. Which means I should have had at least a half gallon left.

Anyone know how big the tank really is?

And is anyone else bothered that the range estimate changes to "LOW FUEL" when you get below ~45 miles? My old GMC Envoy DIC read right down to a few miles. Don't they trust us enough to tell us the truth?!

I've put 12.125 gallons max in my 2008 GXP. It's got a 13 gallon tank

pontiac.com specs say 13 gallons. Everywhere I've looked says 13 gallons.

Maybe something was up with the pumps you go to?

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2008 Mysterious GXP (MoMo)
Solo Mach "Shorty" and Solo High Flow Cat
ADR wheels, XenTec headlights/fogs.
Badges removed, tinted windows.
Pontiac symbol overlays all around.
VIN 100541 - Drove it home 7/13/07. As of today; 26,000 Miles

I've put 13.5 in before, and I've put in just over 13 quite a few times.

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2004 Dodge Ram SRT-10 - 500HP/525 ft/lbs!!

Previously known as "SolScuba"

Most I put in was 12.4 gallons.

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2007 Cool GXP with Darkside Top, 5 spd, Ebony Cloth, Monsoon with Single CD, Sport Pedals, XM, A/C
Mods - Solo Street/Race Exhaust, K&N Drop-in Air Filter, EDAL

Found some info on fuel tank capacity, interesting "Oh, that's good to know" info.

Link

Just in case that link doesn't work for you;

According to the article a tank can hold up to 3% more than the specified tank capacity. That's as much as 0.39 gallons for a 13 gallon tank

Manufacturers rated capacity
Typically the owner’s manual provides a reasonable estimate of your vehicle’s fuel tank capacity. Some manufacturers estimate that the capacity of a fuel tank may vary by as much as 3% from the actual tank capacity. This results from normal variations in design characteristics, the manufacturing process, and other inherent factors. The rating is determined by taking an average volume based upon the capacities of multiple tanks. Furthermore, the rated capacity may include only the usable portion of the fuel tank or it may include both the usable and unusable portions.

The unusable volume is the portion of the fuel tank’s liquid capacity that lies at the bottom of the tank out of reach of the fuel pump. The usable volume is the portion that can be delivered through the filler pipe into the tank when the vehicle is level. The vehicle’s fuel tank capacity does not include the volume of the filler pipe or the vapor head space, which is the portion of the tank compartment at a level above the filler pipe neck.

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2008 Mysterious GXP (MoMo)
Solo Mach "Shorty" and Solo High Flow Cat
ADR wheels, XenTec headlights/fogs.
Badges removed, tinted windows.
Pontiac symbol overlays all around.
VIN 100541 - Drove it home 7/13/07. As of today; 26,000 Miles

10 gallons..

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DDM Supercharger #2
DDM Stage II Intercooler
DDM Pro-Beam
JPM Shifter
Clear Image Long Tube Header
Flow-Thru Cat
B&B Dual Exhuast Muffler
Eibach Lowering Springs
SSB Brakes Front & Back
BF Goodrich G-Force 255/45 Tires

Between 12 and 12.5 a few times.

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Deep, Ebony
O Sol O Mio

Not to be anal, but 3% of 13 gallons would be 0.39 gallons

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'09 G8 GT WOW WEE Liquid Red, loaded, sunroof....no spare tire
'07 Solstice WOW WII Mysterious, Darkside loaded, no smoker package,(how does one smoke doing 140km with the roof down) no mods.....yet

I did 13 once and was sweating bullets the whole time ... Now I fill at 1/4

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#118042 11/18/06 GXP Mean Darkside loaded wo On-Star
MODS: ED IC Pipes, Dejon IC, Magnaflow Catback

#1922 12/03/05
Mysterious Steel/Sand w/ 6-Disc Monsoon
Conv., Pwr & Premium Pkgs A/C LSD Carpet Mats
MODS: GM CAI & CATBAck
Dover DE

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The time has come for the enthusiasts...
NASSOA
Founding Member - Recording Secretary - Northeast
~~~~~~~~~~~~~~~~~~~

The capacities that I have seen in Pontiac literature and magazine reviews are 13.6 and 13.8.

I have run out and when I filled the tank it took 13.7 gal. Take your pick.

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REAL sports cars don't have Back Seats or Automatic Transmissions.

VIN 3919 - Deep, Steel/Sand Leather, AC, Power pkg, Premium pkg, Convenience pkg, Polished Wheels, Anti-lock Brakes, Limited Slip, Floor Mats.

Food for thought!!!

I know all our cars are relatively new but a safe bet is to never run the fuel level to the very end. You can pick up water, sediment, etc from the last bit of the remaining fuel and fuel injectors hate trash!

Frank I

I know what you mean!

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Deep, Ebony
O Sol O Mio

Temp has a lot to do with how much you can put in the tank, you may be able to put 14 gallons in a tank when the fuel is a 30 degrees and only 12.5 if the fuel is 75 degrees. It is a liquid and expands and contracts with the temperature.

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BIX A BEL Cool, Ebony leather, Chrome, loaded, no XM/onstar Founding member of the "Lost Sols Club"
Deposit (1100) - 9/29/05, 1101/1102 - 2 Feb 06, 2500 - 7 Feb 06, 3000 - 8 Feb 06, 3100 - 13 Feb 06, 3300 - 13 Feb 06, 3400 - 14 Feb 06, 3800 - 24 Feb 06 (112544), 4000 - 24 Feb 06, 4150 - 24 Feb 06
dealer expected deliver 6 March, arrived 28 Feb, picked up that night w 3.2 miles on the clock :)
NOT WAITING ANY MORE!

I've put in 13.2 gallons before.

From what I understand there's also a small 'reserve' in the tank that the manufacturer doesn't account for in the rated capacity, unusable amount or tank capacity variation.

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2007 Deep GXP - M5, Loaded w/o OnStar
Mods: JPM Custom Shifter - Stubby Ant - WindRestrictor - Dejon TB Elbow - Dejon BOV Spring - JPM Center Console - JPM Visor Covers - Wester's Tune
Future Mods: delayed due to European Vacation!!

NASSOA Founding Member

Pontiac Sosltice brochure and website say 13 gal approximate.

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2008 Aggressive GXP, 5 speed, fully loaded. Ordered 8/1/2007, delivered 9/14/2007.
NASSOA Founding Member