jQuery not supported.



MPG drop - Gas mileage plummeting

From ~14 mpg to single digit mpg's. Bad gas mileage.

MPG drop - Gas mileage plummeting

Postby arodfan [OP] » Apr 05 2011, 6:41pm

Greetings everyone,
For about the past 5 months or so I have noticed a drastic drop in my MPG's. It used to be that I would average close to 13-14 (pure highway) and around 10-11 around town, heck I even got 15mpg one time!!!. Recently this has dropped to being around 9mpg highway, and around 7 for in town driving...Right now it is empty and I am afraid to fill it up! I only have 238 miles on the trip meter and the tank (34gal) is bone dry! So thats around 7mpg. I am a good driver, I change the oil every 3k with full synthetic 5-30w. Has Nitrogen filled tires. I dont take off hard or ever floor it. Truck is not a spring chicken, but heck 150k is not a ton of miles either!. Truck info: roughly 150k on dash, Hypertech programmer, 4x4, 4:10 rear diff with Gov Lock, and a Tonnneu cover. What do you guys think it could be? Is this a common issue with these trucks? I looked in this forum and on google, really didnt get anywhere. Some things to note: About 9 months ago I went to Tennessee and when I was there I had the oil changed and the mechanic said he found some metal filings..I have changed the oil 4 times since then, havent found any myself. The trucks oil pressure readings go bonkers on the dash, someone said it might be the oil pump? I recently replaced the fuel pump 2 months ago.
This is all I can think of at the moment, if I remember anything else I will update it. Any suggestions would be of great help guys! I knew when purchasing this truck it was not an economy model, but SINGLE digit mpgs?!?! might as well have shopped around for a 454 or an 8.1 liter :( I am seriously considering getting rid of the truck because of this
Original Poster
arodfan
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 14
Topics: 1
Joined: Apr 05 2011, 6:18pm
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: NY Greater Metro
Year: 2003
Make/Model: Chevrolet Silverado
Extra Info: 2500HD 6.0 V8 4x4
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby morganw » Apr 05 2011, 10:32pm

Have you tried running any fuel treatments? I'd also check your MAF screen and make sure its not dirty or oily.
"Gun control is like trying to prevent drunk driving by making it harder for sober people to own cars" -unknown
99 silverado
10 camaro ss/rs
03 600rr
User avatar
morganw
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 136
Topics: 5
Images: 4
Joined: Feb 07 2011, 12:35am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Florida
Year: 1999
Make/Model: Chevrolet Silverado
Extra Info: 1500 4.8L 5spd 4x4
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby oneillt » Apr 05 2011, 11:06pm

Try new sparkplugs and a new air filter?
Image
oneillt
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 144
Topics: 13
Joined: Mar 14 2011, 3:23am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Cape Cod, Mass
Year: 2004
Make/Model: GMC Sierra
Extra Info: 1500 SLE 4x4 5.3
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby arodfan [OP] » Apr 05 2011, 11:11pm

Replaced the plugs 15k ago with plat plugs, airfilter has been a little while since I checked, but will when I go outside here in a little while to change the oil. What kind of fuel treatment are you suggesting? I will check the MAF screen later too..Although worth mentioning I have a scanner and I only get two DTC's, both from when I have originally purchased the truck many moons ago..So no new DTC's as of yet! I am also thinking of running the next few fillups without the Programmer, see if that makes a difference. Will keep you all posted! Thank you for the replies!!!!!!

*Edit:
I forgot to mention that I also need to replace the Exhaust Manifold gasket, and my tranny fluid is due. Do yous think either or would affect mpgs?!
Original Poster
arodfan
Firing on 1 cylinder [L1]
Firing on 1 cylinder [L1]
Posts: 14
Topics: 1
Joined: Apr 05 2011, 6:18pm
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: NY Greater Metro
Year: 2003
Make/Model: Chevrolet Silverado
Extra Info: 2500HD 6.0 V8 4x4
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby morganw » Apr 05 2011, 11:19pm

fuel treatment like injector cleaner. I dont think that a leak or old tranny fluid will affect mileage like that. The programmer was going to be my next suggestion.
"Gun control is like trying to prevent drunk driving by making it harder for sober people to own cars" -unknown
99 silverado
10 camaro ss/rs
03 600rr
User avatar
morganw
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 136
Topics: 5
Images: 4
Joined: Feb 07 2011, 12:35am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Florida
Year: 1999
Make/Model: Chevrolet Silverado
Extra Info: 1500 4.8L 5spd 4x4
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby duane4238 » Apr 06 2011, 12:49am

As far as any other suggestions, here, I don't have any. Others have covered it well. I did have a 2002 2500HD with the 6.0and 4.10 gears. I bought it new and got rid of it at 40,000 miles in 2005. I never got better than 11 mpg. Usually around 8-10 with mostly city driving. And that was on a new engine. I don't think you're going to do any better than you are.
Duane
duane4238
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 145
Topics: 23
Joined: May 07 2010, 10:09pm
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: n.tonawanda, N.Y.
Year: 1998
Make/Model: Chevrolet Silverado
Extra Info: 5L 4x4 Z71 Ex Cab
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby oneillt » Apr 06 2011, 1:38am

Maybe your tranny is going, and you are slipping in your gears? I know this can be an issue in manual transmissions with aging clutches, but with autos? Image
Image
oneillt
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 144
Topics: 13
Joined: Mar 14 2011, 3:23am
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Cape Cod, Mass
Year: 2004
Make/Model: GMC Sierra
Extra Info: 1500 SLE 4x4 5.3
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby Z15 » Apr 06 2011, 1:45am

I been hearing that in some areas of the country they are upping the ethanol content in gasoline. That could account for less mpg. A buddy drives a fuel delivery truck and he claims they have tested some of the fuel and found 18% ethanol when it was only supposed to be 10%. The State of Michigan is allowing 15% or should I say demanding 15%, so I am told.
Mike
Image Dealer

Image
User avatar
Z15
Recognized Supplier
Recognized Supplier
Shifting into Sixth Gear! [L3]
Shifting into Sixth Gear! [L3]
Posts: 2494
Topics: 128
Images: 8
Joined: Jun 02 2010, 7:24pm
Years of membership: 4 years of membership4 years of membership4 years of membership4 years of membership
Location: Hubbell, Michigan
Year: 2012
Make/Model: GMC Sierra
Variant: Denali
Extra Info: AWD 6.2L
Group Membership:
Vendors
Registered users
Servicemen

Re: MPG drop - Gas mileage plummeting

Postby rednick63 » Apr 06 2011, 1:57am

terrible that they are forcing upped ethanol which can damage older engines
No Rest, No Mercy...No Matter What!
User avatar
rednick63
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 158
Topics: 11
Images: 6
Joined: Mar 20 2011, 9:17pm
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Blue Jacket City, Ohio
Year: 2011
Make/Model: Chevrolet Silverado
Extra Info: 5.3L V8 Z85 4x4
Group Membership:
Registered users

Re: MPG drop - Gas mileage plummeting

Postby lohchief » Apr 06 2011, 2:29am

Sounds like at least one of your cats may be plugged or broken.Just sayin'.....
2012 Nox LTZ
User avatar
lohchief
Combustion on 1 piston [L2]
Combustion on 1 piston [L2]
Posts: 163
Topics: 1
Images: 2
Joined: Feb 06 2011, 11:02pm
Years of membership: 3 years of membership3 years of membership3 years of membership
Location: Oregon
Year: 2011
Make/Model: Chevrolet Silverado
Extra Info: 5.3L Z71 reg cab
Group Membership:
Registered users
Servicemen
Next

Return to Vortec 6000 6.0L V8

 

  • Similar topics
    Replies
    Views
    Last post

Common search terms

think miles since check plummeting drop mileage used keep fuel guys bought exhaust make tires great help right rear trucks engine getting

It is currently Nov 01 2014, 12:32am

  • Sponsor
Login  •  Register
SHOP TALK (Live Chat)
Vortec 6000 6.0L V8 Forum
Vortec 6000 6.0L V8 specific
To create a new topic in Vortec 6000 6.0L V8, click this button:
Previous topic Next topic
Sitewide News Sitemaps & Feeds

Who is online

Users browsing this forum: No registered users and 11 guests