terrible fuel mileage - Ford Powerstroke Diesel Forum
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post #1 of 12 Old 03-06-2012, 07:22 PM Thread Starter
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terrible fuel mileage

I have an '01 4x4 automatic with 136000 miles and only getting 10-15 mpg highway. Cortex programmer actually hurts mileage. Any suggestions? I do plan on a cai and 4" straight pipe.
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post #2 of 12 Old 03-06-2012, 07:29 PM
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Do you smell any fuel in the cab or see a fuel leak mine was leaking fuel at the fuel filter housing and when i got that fixed my mpg straightend back out i only get about 14-16
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post #3 of 12 Old 03-07-2012, 06:16 AM Thread Starter
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No...no fuel smell
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post #4 of 12 Old 03-07-2012, 06:43 AM
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Just a couple of questions -
How fast are you driving getting those MPGs?
What kind of HP/TQ are you getting from your Cortex?

I ask because in my truck (see sig), on a recent 500 mile run @ approximately 75mph (cruise set), I got 15.9 mpg. OTOH, once when driving through Oregon on a posted 55mph road, I got 19.2 mpg.

Speed does have an affect.


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post #5 of 12 Old 03-07-2012, 07:43 AM
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Check your map sensor eletrical connections they can come partially unhooked and will dump fuel you will usually see more smoke from the tail pipe.
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post #6 of 12 Old 03-07-2012, 12:15 PM
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You may also wanna check ur fuel filter to see if there is a bunch of gunk in it. Also as said earlier speed and how u drive it will affect mpg. Another thing that might affect it is where u drive.
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post #7 of 12 Old 03-07-2012, 01:21 PM Thread Starter
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On highway I was driving 70-75 with no load. Best was around 14.5. In town with 16' enclosed tool trailer got 1de4.8. Cortex programmer definitely helps power but I get better mpg w/o it. That's what has me confused...
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post #8 of 12 Old 03-14-2012, 03:13 AM
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No tune, chip or programmer will give ou better mileage than stock. Not a one. You'll read advertising like "customers report increased fuel mileage" but there is never any real truth or scientific testing. Marketing bull crap is all it is.

Your mileage is pretty much where most of us are at. You won't get into the 20 mpg ever.

Nonconformist. Functionality over bling.

My three rules for 7.3l troubleshooting: 1) Replace CPS and keep a spare. 2) Replace FPR and know your fuel pressure. 3) Hook it to a scanner and check for codes.
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post #9 of 12 Old 03-15-2012, 05:15 PM
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It's a 8,000 pound if not more truck. If your driving at 70 75 the rpms are probably around 2,200 that's y ur getting 10 to 15. Drop the speed to 65 and u will see a jump.



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post #10 of 12 Old 03-15-2012, 05:22 PM
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Like all said, 15 is about right. Depending on if you get winter fuel or not, you're doing good.
10 is low, but it depends on driving, tires, gearing, lift, load, etc.
There are MANY things to check to help your MPGs.
Brake caliper slide pins, tire pressure, bearings, internal motor, trans, and diff resistance, air resistance, and many other sensors and things that can do it.



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