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  1. #1

    Default Silverado 5.3 Gas Mileage

    I just dropped a 5.3L engine into my Silverado and I'm shocked at the gas mileage I'm getting now. I get like 17-18 mpg while going 80. Is that normal? I have an intake, exhaust and bully dog programmer. My 4.8L that was originally in the truck was getting like 25 so I don't understand why it would be that big of a drop. I was just wondering if that was the normal mileage for you guys out there with the 5.3. Please help!
    btw the engine was out of an 04 Silverado. and I have 3.23 gears in the rear end.
    Last edited by Chad513; 09-14-2012 at 01:13 AM. Reason: added info
    '07 Chevy Silverado Classic

    PERFORMANCE
    -K&N Intake
    -Air Raid Throttle Body Spacer
    -Thrush Muffler
    -Bully Dog Triple GT Programmer
    5.3L V8
    LOOKS
    -3" Spindle Lift
    -Tint
    -Blacked Out Rims
    -Blacked Out Taillights
    SOUND
    -2 Kicker CVT 12s
    -Rockford Fosgate 6.5"
    -500 Alpine Mono Block
    -Pioneer 6.5" Touch Screen
    -2 Boss Tweeters
    SOON!
    -3.73 gears

  2. #2

    Default

    Well its a lil bigger motor with a lil more power, which will result in a drop of mpg and also going 80 with that motor means it needs more fuel which also results in lower mpg. so that is about normal.


    2010 Silverado Z71

    Kyle-USAF-MI/VA

    "Fueled by Haters"

    TCS front box 7"-9" set at 8.5" | FTS coilovers(blue coil) with resis and FTS shocks with resis| 20" Fuel Off-Road Revolver Rims | 35x12.50 Nitto Trail Grapplers | Halo Projector Head Lights by Recon- Black | Led Taillights by Recon- Smoked | Dumped Straight pipe | Volant CAI | Ranch Hand Front Bumper | DiabloSport Trinity Programmer | Tow Mirrors with Turn Signal | Cervinis Ram-Air hood | 4.56 USA gears with tru trac locker | Longshot Lighting 6000k 55w low beam and 6000k 35w fogs HIDs | 7" lift leaf spring | Blue TCS traction bars

    Future Mods: Long tube headers
    | Custom tune | Cam | Stall Converter

  3. #3

    Default

    It scares me lol. I have never seen that low of a number. Your truck is sick btw man. I just joined the Navy and am hoping to do lots of stuff to my truck when I go on leave.

  4. #4

    Default

    I can squeeze 20-21 assuming a flat highway doing 60-65. After 65 it starts dipping fast. 17-18 at 80 doesn't surprise me at all and sounds about right. I've toyed with the idea of dropping a 6.2 into mine at some point. I most likely won't, but if I did I'd expect a 10-20% drop in highway mpg just like you noticed going to the 5.3.

    To Be Completed (Eventually):
    6" BDS Suspension lift | KingShocks Front and Rear Coil Overs | 4.56 Gears | 35" A/Ts (TBD) | Cervinis 07-12 Silverado Ram Air Hood | Fab Fours Front Winch Bumper (CS07-H2051-1) | Fab Fours Full Size Rear Bumper (CS07-W1850-1) | RX-2 Series Main Grille (Black) | Line-x Bed and wheel wells | Skid Plates | Rizor Automated Tonneau Cover | Custom Bed Insert | RBP RX-3 Series Nerf Bars | Kenwood Excelon DNX9990HD | JL Audio Stealthbox (2x500RMS) | JL Audio HD 1200/1 Class D Mono Amp | JL Audio C5-653 Components (Front) | JL Audio C5-650 Components (Rear) | JL Audio Slash v2 300/4v2 Class A/B Amp

  5. #5

    Default

    chad- thanks man. its all deployment in that truck lol.
    jeremy- i thought about a 6.2 as well, once its paid off i think i might hop up to it for the extra power.

  6. #6

    Default

    Chad: what rate did you get in the Navy? I was in the Navy myself. Also, I used to get 22-23mpg driving from Bakersfield Ca to Los Angeles, then I leveled my truck and bigger rims/tires and now i get 19 if I do it right lol. All I have is an intake (the mileage was done via the good ole math method instead of DIC)

  7. #7
    Jr. Apprentice
    Join Date
    Mar 2010
    Location
    Montgomery, Alabama
    Posts
    16

    Default

    I have a '12 Ext Cab with 5.3 and 3.08 gears, a PCM for Less tune, K&N system, magnaflow single in, dual out and 20s on the ground. The absolute best mpg I can get on the highway, running an average of 80 mph, is 15mpg. It would be a miracle to get 18mpg at 80, in my opinion. BTW, I'm retired Air Force myself.

  8. #8

    Default

    corvetteOJ your best bet to help get milage up is new gears. having 3.08 with a 5.3 is causing you to run at a higher RPM which is killing your mpg and having 20s which are heavier is also killing it.. i had 3.42s when mine was stock and average just over 20mpg on the highway. but now that mine is lifted im soon to be running 4.56s...Also what did you do in the AF, im currently enlisted. just hit my 3 year mark in july and am on my 2nd deployment.

  9. #9
    Jr. Apprentice
    Join Date
    Mar 2010
    Location
    Montgomery, Alabama
    Posts
    16

    Default

    Quote Originally Posted by sfdefender24 View Post
    corvetteOJ your best bet to help get milage up is new gears. having 3.08 with a 5.3 is causing you to run at a higher RPM which is killing your mpg and having 20s which are heavier is also killing it.. i had 3.42s when mine was stock and average just over 20mpg on the highway. but now that mine is lifted im soon to be running 4.56s...Also what did you do in the AF, im currently enlisted. just hit my 3 year mark in july and am on my 2nd deployment.
    Thanks man, I appreciate the advice but would rather not start messing with the rear gears while it is still so new (three months old). I agree 100%! I was a little disappointed when I discovered it had 3.08s. Everything else on the truck was exactly like I wanted and I was in a position where I needed/wanted to trade "overnight" so to speak, so I did.

    I did 27 years in the Air Force, enlisted, retired CMSgt. The first half of my career (approx. 14 years) I was a crew chief on fighters, mostly F-4s. The second half (13 years) I was in PME, (Professional Military Education) at various positions, including Commandant for three years.

  10. #10

    Default

    Quote Originally Posted by CorvetteOJ View Post
    Thanks man, I appreciate the advice but would rather not start messing with the rear gears while it is still so new (three months old). I agree 100%! I was a little disappointed when I discovered it had 3.08s. Everything else on the truck was exactly like I wanted and I was in a position where I needed/wanted to trade "overnight" so to speak, so I did.

    I did 27 years in the Air Force, enlisted, retired CMSgt. The first half of my career (approx. 14 years) I was a crew chief on fighters, mostly F-4s. The second half (13 years) I was in PME, (Professional Military Education) at various positions, including Commandant for three years.
    Your welcome man, Im shocked and dissapointed to see chevy is putting 3.08s in trucks now. Makes no sense to me personally. And you are correct with it being so new, i wouldnt wanna mess with the set up just yet. Sounds like you did some major time, thanks for your service. Glad to see alot of active and prior military on here.

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