gas mileage = sad face :(

5377 Views 29 Replies 13 Participants Last post by reggiecab2000, Aug 30, 2011

reggiecab2000

Discussion Starter · Aug 20, 2011

If you look in my signature you could see many potential reasons for my poor gas mileage but I swear its the truth that doing every single one of those things has not changed anything in my mileage it has remained the same...
i used to have just the throttle body spacer and cold air intake and flowmaster exhaust with stock tires no lift and still could never hit more than 15 mpg...
even with gears, lift, tires i still have the exact same mileage which usually varies from 13 to 15 mpg, this is a V6 btw...
my last 2 tanks however have been shockingly awful... ive been about 11.5-12 mpg and i dont know why!
i just replaced my fuel filter, i have recently replaced plugs, wires, cap, rotor, oil, oil filter (fully synthetic for years now), sprayed my throttle body, cleaned my k&n filter....
and i still cannot understand why my gas mileage is so poor i also recently seafoamed my gas tank and, a few times a year i am normally throwing in 44K (dads pick)
But i have noticed over the last few months a minimal (noticeable to me) loss in power overtime and i havent seemed to gain it back yet...
I really am going crazy with a 26 gallon tank that i have to refill after 320 miles.... do the math
does anyone have suggestion/help/comments for me?
I am wayyy past my high school gunnin the gas years and hardly ever beat the pedal unless necessary...
but i am fed up with this mileage.

2000 Chevrolet Silverado

Powertrain:
4.3L V6, 4L60E, 2WD, Single Cab
Performance:
Airaid CAI
Poweraid TB Spacer
Flowmaster 10-series exhaust (dumped)
BLACKBEAR TUNED!!!
Edge CS insight monitor
4.10 gears
Limited-slip differential
LS-1 Dual Electric fans
Corvette tranny servo swap

Audio:
Head Unit: Alpine
Speakers: Alpine SPR-60C 6.5" component set, 4X6 Infinity Kappas
Subs: 2-12" Kicker CVT's
Amps: Alpine-M1000 (subs), Alpine MRX-F65 (Speakers)

Tires/Wheels:
305/70R16 NITTO Terra Grapplers
16" PROCOMP 7089's
Suspension:
2" leveling kit
3" Fabtech Spindle Lift Kit
Front/Rear-Bilstein 5100 shocks

Lighting:
FRONT
35W HID Low Beams
RECON LED smoked roof cab lights
REAR
HELLA LED taillights and 3rd brakelight
HELLA FF-75 Aux. Reverse Lamps
RIGID dually D2, flush mount, wide beam
Accessories:
Hawk HPS Brake pads
Russell braided steel brake lines
Powerstop-red powdercoated brake calipers
Powerslot Cryo brake rotors
EGR in-channel window visors

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tbplus10

· #2 · Aug 20, 2011

I'll probably upset a few people with this post but IMO the reason for your poor fuel mileage is the 4.3.
It's never been a great fuel mileage engine, even in the S series trucks it didnt get much better than what your seeing.
I really think deleting the two cylinders killed the performance of that engine and I've always felt it was underpowered for a full size truck which causes it to work harder and consume more fuel.
As to why your suddenly experiencing even worse performance and mileage? Good question it appears youve done everything to ensure the maintenance is up to date.
Have you checked the compression lately? Maybe the engine's getting ready for a rebuild/replacement.

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tbplus10

· #4 · Aug 20, 2011

The reason the trucks rated at those figures is because GM was under a mandate to produce fuel mileage numbers in a certain categorie.
After a lot of work they got a truck on a test track under perfect conditions to perform those numbers.
So they got their CAFE rating and sold trucks and everyone was happy.
Except the purchasers of those trucks that never got them to perform nearly as good as GM's claims. But to be fair every car manufacturer does this to meet their mandated numbers.
Compression testing is easily done in your driveway, most AutoZones will rent or loan a compression tester.
You'll need to get the appropriate section of the maintenance manual for your particular truck/engine to compare your readings and familiarize yourself with the safety precautions.
The short explanation of the task is remove the first spark plug, put in the compression testor adaptor, neutralize all the other spark plugs so the engine wont actually start, have someone turn the engine over while you record the readings on the compression testor gauge, then proceed to the next cylinder, repeat the proceedure until you've got a reading for every cylinder, compare the readings you have with the manual and see if you have any exceptionally low cylinders.

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