Fuel mileage decrease

T

TxDiesel007

Uncommon CR problemed
Joined
Jul 15, 2007
Messages
1,648
As stated,

my 05 has 185K mles on it as we speak, and has just dropped within the last month from 15-16 mpg in the city, to 12.5-13.0 AT BEST.. highway is no improvement either, im gettin 16-17 highway hand calculated..

only mods to the vehicle are 5 inch exhaust, smarty S06 on level 5, and a drop in AFE filter..

i have already re loaded the smarty, recalibrated the speedo for 33 inch tires, ran it stock, ran it with smarty NO IMPROVEMENT AT ALL even with the smarty, but drivability is much better.... changed the fuel filter on it, and, theoretically.. im out of ideas..

any explanations? or ideas?

thanks

Rick
 
Ur air filter clogged? Do you have an automatic? I was getting 23 avg now 16 b/c my bands are bad.
 
air filter has been cleaned out

its an AFE drop in, tranny just got new solenoids etc etc etc no more than 5K miles ago, no word from my mechanic that anything was that bad, they just needed readjustin..

done the basics too, U joints, brakes, tire pressure, filters, fuel from same station as a constant...

and just added a ton of stanadyne tryin to clean out the tank..

just confused why it would just drop all of a sudden..

thanks
 
sounds like you got a boost leak, even a small one can be noticed with fuel economy.
 
Also a bad injector can do it! Same thing happened to me but I kept driving it and melted a piston! Got any smoke on start up? That was my only clue!
 
dangerous06 said:
Also a bad injector can do it! Same thing happened to me but I kept driving it and melted a piston! Got any smoke on start up? That was my only clue!
Click to expand...

YEOWCH

smoke on start up, none that i can tell, and meltin a piston is not what i want to know...

ill really look, but truck starts, runs great, and i know its only got a light haze when idlin, but im assuming due to the smarty...

anyway to test injectors or see if they are bad? i get no codes from the injectors or engines, as of 8am this morning
 
just a light puff of smoke when it starts up

no white, not dark, just a light grey at best, truck runs and idles fine, and it does have a light haze at idle, not like 370s, but lighter, unless its the heatwaves here..

MPG calculator right now says 13.5 mpg combined, on 33s with a toolbox, tank, rack, bumpers etc... so im assuming its close to normal then? ext cab long bed... 3.73 rear end?

so what could be causin my haze at idle then? im stumped

i dont trust the mpg calculator, but hey its appearin to be pretty accurate as of late
 
is yours a single wheel? what trans?

I have the turd G56 that is ridiculously low geared, plus dual wheels, plus larger ones at that, made for about the same mileage you are getting. Now I am converting it to a single wheel auto, see how it does...
 
in either case

im guessin from past experience a lil smoke at start up is normal, my 12v did, so im guessin its ok,

mines an auto with a single rear wheel, FWIW...3.73 rear end

im just stumped as towards why my mileage sucks compared to my old truck...
 
Smoke at start-up is normal, but it really shouldn't smoke at idle with stock injectors. Where in Tx are you at?
 
I found 2 boost leaks last night hopefully it will help my mileage

Sent using tapatalk from my HTC Aria
 
Pull your injectors and send them in for testing I bet one is bad! Isaac at freedom diesel has a fast turn around but expect to here your injectors are shot! So get about 2 grand together and don't get over 60hp sticks if your concerned with milage I have the 90hp sticks and dropped about 3 mpg no matter what i do!
Oh and get a 2 micron filter pre CP-3!! It will save your injectors in the future!
 
Any haze out of an 05 is probably at least one bad injector. As said earlier if you keep pushing it you could be looking at rebuilding an engine.
 
dangerous06 said:
Pull your injectors and send them in for testing I bet one is bad! Isaac at freedom diesel has a fast turn around but expect to here your injectors are shot! So get about 2 grand together and don't get over 60hp sticks if your concerned with milage I have the 90hp sticks and dropped about 3 mpg no matter what i do!
Oh and get a 2 micron filter pre CP-3!! It will save your injectors in the future!
Click to expand...

yesterday

turned on the truck, and sat by the exhaust pipe, i thought i saw a haze, but in actuality it wasnt, i sat there for a while and let the truck run, and nope no haze... none of these symtoms either...

very light puff of smoke (grey) at first start up
no loss of power,
no blowby on under carraige
no making of oil as they say
engine bay is completely clean
no blowby from turbo either..

just got done starin at my exhaust pipe again... i dont see a haze...

but im guessin at 185.5K miles, the stock injectors have got to go already... probly if they arent shot, they are close to it...

so i can see the point of musterin up 2K dollars for new ones..

thank you very much!
 
in all seriousness

too many variables in this one.... part of me saysim just gonna chalk it up to a bad tank of fuel, a wonky calculator, and another part of me states all the crap ive added to the truck most certainly cannot help it out in the mileage depot..

toolbox
110 gallon tank
headache rack
full front bumper
full rear bumper
side steps
285 sized muds

seems to add up in the weight depot, so im guessin thats gonna kill this thing

but in all seriousness, if i HAVE TO pull injectors to test them out, shouldnt i just replace them at once and be done with it?

and how long are stock injectors supposed to last? truck has not been modded other than a smarty at all... and tahts only been 5K miles ago...

my dads has a superchips in it, as well as a built tranny, AFE stage 2, and a 62 mm charger i believe from Industrial injection, and it gets 21-23 on the highway.. and is the same as mine,

FWIW trucks still on.. went outside, no haze out of the tailpipe... no diesel fumes either, and cannot feel the heat from the five inch exhaust past about 3-4 feet from the pipe...

truck idles fine, no leaks, nothing..

yesterday goin to work tho, i did reset the mileage calc, and at 70 mph, the calculator read between 18-19 mpg... then it steadily drops when im idling to as low as the mileages i state... it does not seem to go up at all past 13.. i reset it while im in motion and i get the best mileage.. other times it goes from 0 mpg up by 1 tenth of a mile till it hits 13.. others it works backwards (ie when im in motion)

was gonna buy a Dr P module.. now im goin filter instead... 2 micron?

anyone got a reasonably priced setup? it dont sound like some kit that they just sell... and filter numbers too

thanks
 
At that mileage it wouldn't hurt to test the injectors, if you can do the work and stand the down time. However, I wouldn't replace them just because.
Better filtration is always a good idea. You can get a kit from a shop like Glacier, or make your own for pretty cheap. Fittings and hose from Summitt (for example) and a filter and head from a big-rig shop.
 
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