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  1. #1

    Default How big is the fuel tank for 2008 Silverados?

    When my salesman sold me my truck he informed me the gas tank was smaller this year and was 21 gallons, but after filling up a few times, I have put in 22 gallons plus. I was reading and saw that it still is 26 gallons. If that is the case does anyone know when the fuel light comes on how many gallons are left? I am trying to figure out my mpg before I put on the CAI and the Fitch Fuel Catalyst.

    08' Silverado Ext. Cab
    Texas Edition
    Flowmaster 40 series duals
    Windows tinted 5% all around
    Remote start
    Garmin nuvi 260 GPS
    K & N Air Flow
    Sirius Stilletto 2 Radio

  2. #2


    Obviously, your salesman got his facts confused. Rest assured, this is nothing unusual.
    For calculating MPG, you're assuming too much accuracy from your low fuel warning. It's going to vary with each individual vehicle. What you want to know is how many miles can you go with the gas remaining. Doesn't your owners manual give an estimate?
    To accurately determine the gas left, drain the tank immediately when the light comes on. However, that's a pain in the butt. You can fill-up when the light comes and subtract the amount from the total capacity, but then you're guessing that the total is 26-gallons. It's going to be close enough to calculate additives. But, if you really want more accuracy, than a 26-gallon guess, you can determine your usable capacity by running it dry (another pain in the butt, but pushing is easier than draining) and then fill-up.
    Are we having fun, yet?

  3. #3


    Good advice. I guess I was not being meticulous enough when i figured mine. I just filled up, all the tank would hold and set the trip odometer and drove till I needed gas and filled the same way and used the miles divided by gallons method.Worked for me.
    Chris S. The GoFastPadre I like to drive fast and I've got the speeding tickets to prove it. 00 Sierra Z71 ECSB K&N CAI Pacesetter Shorties (soon to be replaced with LT's) Magnaflow HFC's Flowmasters with True Duals and H-Pipe more mods to come

  4. #4


    My understanding that there are two tanks in the NBS's , the standered one and a big one optional only, the standered one is the one you and me have on our trucks, and I am sure it is more than 90 Leters because I filled it with that, and this is around 23 gallons, and I guess 26 gallon is the size of the tank.
    I drove the truck around 20 Miles after the low fuel worning and it didn't stop,and I guess that is more than needed to find a gas station if you are not on an offroad trip and in that case you should have addetional gas tank with you.
    Don't leave your normal tank less than 25% remaining, evryone says that's a bad thing to do since all the dirt and remains in the tank will go into the car fuel system.
    2008 Sierra SLE

  5. #5


    Quote Originally Posted by GoFastPadre View Post
    I just filled up, all the tank would hold and set the trip odometer and drove till I needed gas and filled the same way and used the miles divided by gallons method.Worked for me.
    That's what most everyone does. If you're a real stickler, then you can apply a correction factor to your odo reading. If you drive where they have a long road side speedometer test (or accurate mile markers) then you can compare what your odo reads to the actual miles. That will give you your correction factor. With the tires I have now, my odo is off by 1.5%. When I calculate my MPG at 20.0 it's really 19.7.

  6. #6


    26 Gallons. You can get an option 34 Gallon tank if you have the extended (8') bed.

    And don't run your tank dry to determine your mileage. Fill up. reset trip meter. When you get near empty, fill up. View # of miles driven on trip meter and divide by # of gallons in tank you just filled up with. That gives you your mpg.

    If you've changed from stock tires, get your speedo recalibrated.

    Other way you can check speedo accuracy is if you have a gps unit. ;)


    '08 Chevy Silverado LT2 Extended Cab - AVS Hood Deflector, BedRug Mat.
    '06 Chevy Equinox LS - Stock! (Wife's car)

  7. #7


    Quote Originally Posted by branhap View Post
    And don't run your tank dry to determine your mileage.
    The suggestion wasn't to run dry to determine mileage, it was to determine the actual capacity of his "26 gallon" system.

  8. #8
    Sr. Apprentice EKperformance's Avatar
    Join Date
    Oct 2008
    lake City Florida


    the driver info center is pretty accurate, if you dont have on e you can buy the pannel and buttons for less than 100 bucks, the harness is already there just plug it in and your done
    2002 silverado 4.3 5spd / off road y pipe, flowmaster split duals, K&N filter
    ported throttle body , ported heads and intake < all by me

  9. #9
    Sr. Engineer zach45's Avatar
    Join Date
    Apr 2008
    staten island new york


    yea im suppost to be 22 but i have filled about 29
    08 5.3 silverado...toyo m.t 33 12.50 18 rockstars...leveled with 2" blocks...cherrybomb catback...6k hids

  10. #10
    Jr. Mechanic
    Join Date
    Oct 2008
    ST Louis MO area


    My low fuel light came on and i went about 13 miles on the hwy.When I filled it up it took 25 gallons.So I wouldnt go too far when it comes on you will be walking or calling onstar.

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