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Discussion Starter #1
Hey everyone! I'm sorta new to the diesel game so I'm here to ask advice from you experts!

I have a '03 F250 4 door short bed 4x4. Ive been getting awful fuel mileage lately and I'm unsure why. Heres a list of everything I've checked/replaced:

EBPS and tube - cleaned
Replaced all things brakes - nothing stuck
cold air intake - replaced filter
315/70/17 Cooper discover M/T @ 60 psi
4" exhaust from headers back
Fresh oil change with rotella T5
New glow plugs
Edge programmer on tow tune
Add a bottle of standyne to every tank

After checking the obvious, I'm still getting 9.4 MPG. No load, DD usually 10 - 15 miles per day and speeds averaging 30 MPH and I accelerate lightly. I understand that these trucks shine at 55 MPH but that's rare up here in Alaska. We just switched from winter blend to summer blend diesel up here but I didn't see a difference in performance or fuel efficiency.

Any suggestions?
 

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welcome to PSN.
you did not mention axle ratio, but even without that i can tell you the tire size is not good for mileage. also, the edge tuner is not helping either.
my untuned 02 with 265/75/16 tires gets 12-13 at 45 mph.
 

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I would check to make sure that none of your brakes are dragging. The calipers in these trucks suck. Also the slide pins freeze up and make the pads drag.
 

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Discussion Starter #5
welcome to PSN.
you did not mention axle ratio, but even without that i can tell you the tire size is not good for mileage. also, the edge tuner is not helping either.
my untuned 02 with 265/75/16 tires gets 12-13 at 45 mph.
Yeah I'm unsure of the gearing. That's one thing I plan on looking into this summer. As for the tuner, I actually get worse mileage at stock.

I would check to make sure that none of your brakes are dragging. The calipers in these trucks suck. Also the slide pins freeze up and make the pads drag.
I just replaced the whole brake system about 2 months ago and checked last weekend, nothing sticking.

Check for boost leaks.
I'll for sure do that. Is there any way I can do this or does it require a shop/special tool?
 

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Google/Youtube "How to make a boost leak detector", several different ways to go about it, but pretty easy/straight forward.
 

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FWIW, i have basically the same truck, same tire size with a PHP Hydra tuner, Tony Wildman economy tune. Im getting a fuzz over 16mpg in town, fuzz over 20mpg highway. I never got much over 12mpg with ANY performance or towing tunes
 

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Is the thermostat stuck open and not letting the engine fully warm up? That will kill mileage when everything else
is fine.
 

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Several things.

Presumably, you are right on top of your rear brake slider pins (I clean and lube min e every other oil change. Otherwise they drive me crazy. If you care about MPG, dragging brakes are the kiss of death.

The obvious. Your big tires are killing your MPG. They may be a necessity in Alaska.

My EBPV never would work in cold weather. From November to May I heard that blowing sound similar to that of exhaust brakes, so I electrically disconnected mine (in July). No seasonal variation in EBPV but it takes about 20 miles to warm-up on a January morning in Indiana. Block heater mitigates this somewhat. But if you are satisfied it is working OK, move on.

I don’t know about Alaska winter blend. Alaska is a special case. What you get in summer may pass as winter blend in the Midwest. Here we get a 20% blend of #1 middle distillate about three months a year.

Something to consider: Air density. I know in Alaska aviation is important. Ask a pilot about “density altitude.” If he knows his stuff, you’re in for a two hour dissertation. I heard of a cold snap a few years back (cold enough to impress Alaskans at Prudhoe Bay) where the density altitude was – 14,500 feet. That’s right the same as “normal conditions” if you were three miles underground. Low density altitude is life to bush pilots. It’s Mother Nature’s turbocharging. Engines 9onc warmed up run very powerfully as they are sucking in more oxygen than standard, and lift surfaces work much better at low density altitude. It allows bush pilots to take off with outrageous loads and land on really short strips. But aero drag is proportional to air density. Aero drag is a big component of road load.

Poor MPG may be one more price to pay for living in Alaska.
 
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