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  1. #1

    Default 1988 GMC 1 Ton 3+3 cab 454


    New to this thread, but I just bought a 88 GMC 1 ton 3+3 cab truck with the 454 in it. So far I love it, drives like a dream. My only problem is that I am only getting about 7MPG without a load on it. I guess my real question is how do I get it in the 10-13MPG area. I don't raw dog it, I am not pulling a trailer with it, just picking the kids up from school and doing errands. Do K&N air filters and Lucas gas treatment actually help or are they useless? If y'all need the specs on the tranny and rear end I can pull them. I know a tune up wouldn't hurt, just seeing if anyone has some helpful hints, like putting the max air pressure in the tires(my brother swears by this trick in his 2004 Silverado) but i have no clue if he is just delusional or if it actually helps. Thoughts?? I have also read that fuel pressure regulator could cause horrible gas mileage. I have only ever worked on old Chevy quadrajets. Thanks

  2. #2


    If you bought the truck I would start with the basics, spark plugs, wires, FUEL filter, cap/rotor, clean throttlebody, DON'T use carb cleaner, use a throttlebody cleaner. Change ALL the fluids and run some fuel system cleaner like Seafoam. Run the Seafoam BEFORE you change your oil so you don't contaminate the new oil . You can also use the Seafoam to clean the throttlebody and pour some in a vaccuum line to clean the upper end. Check your fuel pressure. How many miles on truck?

  3. #3


    105K. Which vac line should I pour the seafoam in. I have used it before, just dumped it in the gas tank though.

  4. #4


    PCV or brake booster line.

  5. #5


    He's right about keeping your tires pumped up, also take extra weight out, change all fluids to synthetic helps a little too.
    1998 K1500 Ext. Cab 4.3 5spd
    Amsoil, CIA

    2007 Harley Davidson Vrod
    Amsoil, Vance & Hines 2into1, K&N Topless,
    Screamin Eagle Racetuner, StageII cams,
    Carbon fiber front fender, and a few more lil goodies:wink:

  6. #6


    Welcome aboard and congrats on your truck purchase. I hope you're able to improve that gas millage. Good luck!

  7. #7

    mfleetwood's Avatar
    Join Date
    Jul 2010
    Denver, CO
    Blog Entries


    Welcome to the Club!!! Check out this link....You'll find some great ideas here.

    Mike (Denver, CO) - 2008 Sierra 1500 Z71 SLE 5.3L 4WD

    SUSPENSION: Rancho 4" Suspension Lift; Rancho RS9000XL Shocks; Rancho Skid Plates; Rancho MyRide Wireless Shock Controller;
    BFG All Terrain KO 315/70/17
    DRIVE TRAIN: 4.56 Gears; Detroit TrueTrac Differential; True Cool 40k Transmission Cooler
    PERFORMANCE: DiableSport Predator Tuner; Custom Tuned by Diablew; Magnaflow Exhaust; AFE Cold Air Intake
    ELECTRONICS: Kenwood DNX6180 Touchscreen; Subthump box w/10" Kicker; Driver Information Center (DIC); Rear View Camera
    ACCESSORIES: Westin Brush/Grill Gaurd; Westin Nerf Bars; Truxedo Tonneau; 20% Tint; Tow Mirrors w/Heat & Signals

  8. #8


    Sorry I forgot, welcome to the club.

  9. #9


    Welcome to the Club! You'll find your answers here if you keep looking and asking!

  10. #10
    stephan's Avatar
    Join Date
    Sep 2010
    Far West, Oregon USA,
    Blog Entries


    Welcome to the club Jim. When you're doing your tune be sure & check the compression or do a cylinder leak down test. One low hole can kill your MPG.
    1988 Chevy C-3500 2wd (no pic)
    350 c.i. 5.7 L Stock Block, 4 Bolt Mains
    L-31 Vortec Heads, Edelbrock Cam & Intake,
    Holley 650, Flowtech Headers, Magnaflow exh.
    Jet Trans 700R4, B&M Ratchet, 4:10 gears,
    3" susp. lift kit "shadetree"
    No rev limiter, No speed limiter lol

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