coontz0473

Guys,
I've got a couple of ???'s. I'm not one of those guys that complain my truck doesn't get 20 mpg, but I am wondering what has happened to my mileage.
I have been getting @ 18-19 mpg for almost a year, even after putting on the new tires.
Lately I have only been getting 16mpg!!! I haven't changed a thing. I change my fuel filter on regular basis, I keep my air filter clean, I always buy my fuel from the same truck stop, my driving style is the same, even started using fuel additives to try and get the mpg back - no luck????
What do you think is going on? I thought fuel mileage would get better the more miles I have on the truck (which is @40k now), but I can't figure for the life of me where my other 2mpg went...
Like I said I'm not complaing to have 16mpg, if I would have wanted 20+mpg all the time I would have bought a Geo, but I'm just trying to figure if something is wrong mechanically or about to be wrong. It seems the truck has settled in at 16mpg - been that way for several tanks now.
Is this the mileage I should expect from now on, or is something going aray??
Anybody have any comments??? Thanks!

larryt

No expert here, as I only have not quite 30,000 on my 'o5.

Some things to ponder though:

1. Did you install your afe and run it a lot/mostly in cold weather?
And now you have went though a HOT summer where your
mileage has dropped? Possibly the hot underhood temps are
part of the problem.

2. Would have guessed the bigger tires might be part of it but
you say not.

3. You might hose out the radiator and intercooler coils to clean
out any bugs and debris.

4. It could be a very good idea (for all of us) to run a good cleaner such as SeaFoam thru it in case your injectors are
collecting carbon from not running it real hard.

5. Last but not necessarily least, if you are the curious type and
don't mind doing a little experiment, go back to stock air
cleaner system for a couple weeks. Use a clean element and,
better yet, cut a 4" hole in the bottom and pipe it straight
down a couple feet.
This will give you cool outside air compared to the engine
compartment air.

Item #5 paid off for me. I was running a Fleetguard AH1141
air cleaner using the hot air under the hood. I had noticed
this Summer my mpg had dropped about 1mpg. I blamed
the hot weather. After about 15,000 mi on the element I
decided to change it to a new one.
I picked up 1.26mpg by doing so.
example:
Last 2564.6mi w/dirty AH 1141, 130.6gal, =19.64mpg
439mi w/clean AH1141, 21gal, =20.9mpg =+1.26

I then went back to the stock airbox and installed the new
Donaldson EaA189 drop in filter and a 4" bottom intake hose.
628.3miles, 28.48gal, =22.06mpg= +1.16

Now, that last item needs a little clarification because it was
driving on some county and state roads at about 55>60 mph with the specific goal of trying for the best mpg.

For me the bottom line was cooler air and less restriction. Maybe that will help you too.
Larry

BigDave12768

It's called winter diesel!!!! We all lose fuel mileage in the winter

Jus Cruisin

larryt

Please explain your air box mod a bit more. I have drilled a half dozen 3/4" holes and have noticed nothing. The 4" is interesting. What kind of tube/hose and what was used for the hole?

bry@n

Every winter, my fuel mileage goes down at least 2mpg. This is the same whether it's Diesel or Gasoline.

The prior poster is correct with the Winter mix.

BigDave12768

Drilling holes in the airbox works OK. But you have to have K&N type filter to notice the difference. I did it on my old truck. I used a 1in hole saw. Worked out well.

MikeyB

Could be ULSD fuel. A few of us has notice a drop in fuel economy lately due to the new required fuel.

MikeyB

Patriot2500

I noticed my fuel economy going down the last 2 fillups. But hey, I'm not complaining about getting 550 miles per tank and it lasting me over a week.

kully560

its not the winter fuel I think it does not come out till 11/1 I been thinking the same thing I am down about 1.5 mpg since july and no changes to my truck and I also run howes cleaner in every tank.I just check my ball joints and have play in them at 78000 miles so I wonder if the alinement is out enough to throw off the tracking, long shout, tires look good but I rotate every 6000 miles so I will be doing ball joints and why I am there front ujoints, also and good alinement.I was happy with my 19 mpg on the highway for the first 70000 miles the last 8000 it drop 1.5 so I want it back also kully