for some reason lately i have got awful milage, i have 235/85/16 tires, a 3.54, a tonnue cover if it helps any,a locking gas cap ( just in case), new air filter, new oil, and the only pump adjust i have done was turn the fuel pin just slightly. bit in mostly highway driving, with very few WOT moments, and with a double shot of PS every tank,and mainly weather from 20's all the way up to the 70's around here, and i only got like 16MPG . what gives, at 2.59/G i need all the MPG i can get, and the previous owner got up to 26, on most tanks, which was one of my selling points for buying it, is this all in the valve adjust, why im losing it all, . please i need all the help i can get, i am willin to spend some up from money if i have to, but i need back the MPG's

 

my 92 is basically the same truck as your. with a cap on it i saw as high as 25mpg on one trip a while back. i haven't seen it in a while and have wondered why. across the 4 trucks i've had lately i've seen lower mpg... anything to do with the new fuel? start with the simple things, when's the last time the fuel filter was changed? also 16cm housing(i believe you are planning) and a timing bump will help.

 

HMMM..... Does the engine seem to be under more of a load at all?? Anything smellin warm? Id check to make sure your rear has the proper amount of lube, check to see if any brakes are hanging up. I cant imagine a valve adjustment would throw off mileage. Check that your intake is free and clear, a rag or bird or something could have gotten in there. Give the turbo a spin free hand and see if there is any resistance. That is kinda puzzling.

 

I got 20 mpg in my truck when I first bought it, but haven't seen that since. In combo city/highway driving towing light loads (3500-6500#) about half the time, I was getting about 16-18 before the valve adjust and new filters everywhere. I haven't checked it since then. But mine is a 4WD with a heavy steel flatbed, too. It weighs over 8000# with me, a full tank and the job box on.

 

I hate to bust Gomer's bubble but I haven't SEEN an automatic
get 25 mpg. I can see some of the 5 speeds get it BUT very few.
You also have to remember the "new" ULSD garbage were forced
to use. Again the WOT's will kill any mileage you expect, heavy
right foot will also kill the mileage, I got one of them.
IF you drive like Grandma you will see an improvement.
One more, I think you are using too much PS. The double shot
is not what they said to use all the time.

IMHO

59

 

A locked up fan clutch wouldn't help much eather.

 

He was lying like a used car salesman.

Do the 1/8" timing bump, that will help. Run as much tire pressure as you can stand. Keep the speed down.

 

I've lost 1-1/2mpg since the fuel change,right now I'm hovering right around 19mpg half city half hwy.I use ps at each fill up ,seems to help a little. marc

 

I was averaging 22mpg's. Then I went to bigger tires 285/75 R16 vs. 235/85 R16. I figure that plus the new fuel we're running, plus it beng the winter time has dropped me down to 18-19mpg. Keeping your foot out of it helps as well

 

I have heard from some local truckers that there are different pumps available at the truck stops and that these pumps have different grades of diesel. The ULSD is not going to be good for anything so if there is a pump with the LSD then I would try fueling up there and run a couple of tanks and then see what you get. I have just checked mine and it is the second tank I have personnaly run through and it was around 16 but this is an accurate guess as my speedo is whacked from the larger tires.

 

I did forget about the ULSD
I lost 1 MPG running that out in Cali. when I owned that Freightliner. N lemmie tell ya, that HURTS! I imagine the ULSD isnt helping much.

Yeah i agree, id check the fan too, that'd kill mileage as well

 

Check it....and just throw it in the bed like I did

 

26mpg is a bit of a stretch for an auto, IMO, but then, with my Mom's dually, I got 22-23hwy all the time empty @65mph. SO, figure 1-1.5mpg for the xcab, another 1mpg for the duals, and 25-26 may be obtainable. It hasnt seen that since coming to MO 7 years ago. It got 22 on a trip back west a few years ago.....

I see no reason to get less than 20mpg hwy with reasonable driving (RPM wise) and a Cummins, period. 4.10s require patience to achieve good MPGs. A valve adjustment can make a 3mpg difference if they have gone a long time. Injectors not up to snuff have cost me 4mpg in the past. Not new upgraded, just stock ones cleaned and re-set to stock pressures.

Daniel

 

well i can see how some would think it but i bought it off my Grandpa, a preacher, but i only run about 60 ish, and 95% or more of it is highway. and i am still using the LSD, but how much is too much PS i just use about 1/2 a bottle per tank. could it be my torque converter, and would a fuel filter have anything to do with it?

 

'scuse me while I take my foot out of my mouth.

I don't know why it's doing so poorly. Mileage typically drops in the winter, but not that much. You are driving slowly enough. Is the OD working? What are your tire pressures? What sort of tread? (that does make a difference).

A valve adjustment won't hurt if it's been a while. The fuel filter won't hurt mileage.