Poor mileage.

[thx997303]

I have only managed to get as much as 12 mpg in my truck so far.

I have so far changed a filthy air filter, and replaced the fuel filter.

The truck runs fine, isn't really lacking for power, and the EGT gauge doesn't show anything abnormal according to the forum.

I also drive the thing slow. I'm really not in a hurry to get anywhere.

I would like to verify timing, but don't have the equipment. Not sure where else to look.

Might add, the truck has 4.10 gears, and an E4OD. This 12 mpg number is mostly city driving. The tires are 285/75/16.

Edited to add: The temp gauge never gets past the R on normal for some reason, and the oil pressure gauge tends to stay either on the N or below, but still in the larger zone. Not sure if there's a problem there or not, but thought I would mention.

Edited once again: When I spin the fan on my engine by hand, it doesn't spin more than maybe a half turn. Feels like there's some decent resistance there. And all of the passenger side braided return lines are wet with diesel, and one of the driver's side injectors is wet. I'll be fixing that later. Might be contributing to the problem.

 

[79jasper]

The oil pressure "gauge" is really a dummy switch. Once it hits like 7 psi, it moves the gauge to a preset range.
Notice how it doesn't move from idle to redline??

I'm not so sure the temp gauge works any different....

Are those stock sized tires?

Timing will affect your mileage the most..

 

[thx997303]

They're not stock tires, but they are comparable in diameter to stock, just wider. I intend to put stock 235/85/16 size tires on it when I have the money for new.

I wish I had the equipment to check the timing.

Anybody in the salt lake valley in Utah have the stuff to do it?

 

[79jasper]

Wider tires create more "rolling resistance" and actually "wind resistance."

As far as timing goes, speak with Gary (icanfixall).

 

[jwalterus]

4.10's, auto, city driving, and 12mpg?
why complain???

 

[Greg5OH]

4:10s will help out in city driving vs 3.55s actually, easier for the truck to get going. They hurt on freeway because engine is revving higher.

 

[tanman_2006]

4.10's, auto, city driving, and 12mpg?
why complain???

Kinda what I thought, 235/85's will help in town but hurt on the highway. 285's are ~33x10" and 235/85's are ~32x6". 285's also weigh a quite a bit more which hurts in town with more weight to get rolling. 255/85's are 33x8" and weigh less than 285's, IMO best of both worlds if you can find them in non-mud grip.

 

[thx997303]

Managed to get almost 13 mpg all freeway. Turning just over 2k rpm at 65 mph.

There has to be something going on, the mileage should have been at least a little better than that on the freeway.

 

[gatorman21218]

Timing makes the biggest difference. All the other stuff doesnt matter much. So before going nuts check your timing

 

[thx997303]

I am working on getting a hold of a timing meter right now. Rent one soonish I guess.

 

[Mulochico]

And all of the passenger side braided return lines are wet with diesel, and one of the driver's side injectors is wet. I'll be fixing that later. Might be contributing to the problem.

Any fuel leaking is fuel unburned. When I did my return lines (not "a super wet) my mileage improved approx 1 mpg. If yours are "wet" it might improve more.

When I finally timed it (original, running well, it was at 3 deg btdc. Proper is approx 9 deg btdc) it helped a few more. The problem I had was that when timed properly it had more power, thus I tended to use more of it. Lowering the mpg a bit.

 

[thx997303]

Well I'm gonna start at the injector return lines. The lines between the passenger side injectors are weeping when the truck is running, and one of the injectors on the driver's side is leaking from the cap, bubbling and all while running, so that could be some of my issue.

 

[Black dawg]

Like said, timing can be important. Fuel leaks also. Also check accuracy of odometer, dont assume accurate speedo means accurate odo.

12 in town isnt terrible, 13 on the highway seems a little low, but I have seen that and less out of my truck on the highway. The best/worst unloaded mpg out of my truck is 22 mpg (drove 1000 miles with no stops other than fuel) and around 9 (winter driving, short trips, and lots of 4x4)

 

[chris142]

I've managed 15 MPG hwy with my 3.55's if I really pay attention to my driving. Running 80 across arizona last month I got 12.5 mpg. In town the most I get is 13.

 

['94IDITurbo7.3]

^^^^keep it at 60-65mph and you will see 20-21mpg.......

i get about 16-17mpg driving around town in my truck......turbo, 2wd, 4.10, E4...

timing is a bit retarded as well on mine.....fuel additive plays a role in mine at least....i normally use the white bottle of power service in the winter, but a guy at work gave me a gallon of opti-lube last fall and i used it all winter and about two weeks ago finished it off. right after not using it i noticed a drop in fuel range from my tanks.....