Poor fuel mileage

Trucknut661 · Aug 31, 2017

So I have a 02 7.3 srw powerstroke 4x4 with a 10" lift on 40's with 4:88 gearing. Right now I'm averaging 200 miles on a 35 gallon tank. I was wondering if this mileage is normal or if it's too low. I have stock injectors and upgraded turbo housing. Modification are listed on the bottom. I did also add a redhead gear box and cross over high steer. I've just rebuilt the whole front end and put brand new tires on it. Any help much appreciated

. I know not to expect the greatest mileage so before someone throws that into this.

Magnum PD · Aug 31, 2017

With those tires and gearing, it's a lost cause getting good mpg.

CarportMechanic · Aug 31, 2017

I put in about 35 gallons when I fill up and average about 550 - 600 per tank.

35's with 3.73 gears for me.

Ultimately you should be turning less RPM's when going 70 mph vs me.

I dont see why your MPG would be that terrible.

I know you most likely wont get 16 to 18 mpg but dont see why 13 to 15 couldn't be reasonable.

Your currently getting about 5.7 MPG........

Trucknut661 · Aug 31, 2017

Carport mechanic that's exactly what concerned me when I started doing the numbers.

CarportMechanic · Aug 31, 2017

Id check out your EBPV tube going from your passenger manifold to the front of the motor just under the HPOP gear cover. If clogged will cause low MPG issues. Could also be the sensor itself.

If you have AE you can monitor you Exhaust back Pressure to see if its even working correctly. I know the Torque Pro app works for this as well.

Could be boost leaks as well. Do you monitor your boost PSI? What can you hit max on a full throttle pull?

Has MPG always been this bad? Or recent? Did you do anything to the truck recently?

Trucknut661 · Aug 31, 2017

On full throttle no trailer I'm pulling between 10 to 12, I purchased this truck in Dec and didn't really drive it because I had a lot to fix I just got new tires, alignment, front end suspension done and oil/fluid changes so this is really the first time I'm calculating mileage with everything being service and replaced on it.

PSD POWER007 · Aug 31, 2017

Your odometer is nowhere near accurate I'm sure.

Trucknut661 · Aug 31, 2017

I've had it adjusted already so it's accurate. Plus I use the gps on my phone to compare the mileage to make sure it's accurate when I got it done. Had to take it to a shop so they could input all my vehicle info and upgrades.

Arisley · Sep 1, 2017

Sounds to me like the first place to start would be boost leaks.

Trucknut661 · Sep 1, 2017

My buddy's dad is a diesel mechanic and made some room for me Thursday at his shop. Hopefully he finds out what's going on.

TjMiller · Sep 3, 2017

Is that highway, city or combined milage? Is the converter locking ?

Chris2590 · Sep 5, 2017

It sounds stupid but is your air filter clean? I can tell a difference in fuel mileage if mine starts accumulating dirt.
Also how long has it been since you've changed the fuel filter? And like said above if the ebp tube is clogged you'll get ****ty mileage.

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Chris2590 · Sep 5, 2017

Oh and check for soot around the exhaust. If you have leaking up pipes you'll definitely lose mpgs

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Trucknut661 · Sep 5, 2017

That's city, the converter is locking, no slips or anything on the rpms, the air filter I blew out with air, the fuel filter was a little dirty and changed that out. I change the fuel filter every 9000 miles (every 3rd oil change). I'll check for the soot and see what i find

CarportMechanic · Sep 5, 2017

Trucknut661 said:
That's city, the converter is locking, no slips or anything on the rpms, the air filter I blew out with air, the fuel filter was a little dirty and changed that out. I change the fuel filter every 9000 miles (every 3rd oil change). I'll check for the soot and see what i find

FWIW, 3k on the oil changes is pretty frequent. Not bad but more often than most 7.3 owners. You can get away with 5K. Then do fuel filter every 2nd oil change. Save you a bit of cash also.

Trucknut661 · Sep 5, 2017

I was only doing it that way because ford recommends changing the oil every 3k miles and the fuel filter every 10k. So this being my first diesel I just went with what they said. Thanks for the heads up though

dmd · Sep 5, 2017

Motocraft oil filter are $10 at Walmart, change it every time or you are adding two quarts
of dirty oil to the clean oil. Given the HPOP system has oil left in it, but get out what
you can. Oil is cheap insurance..

ALSO, per Ford you do not want to use the the "CK" rated oil. You need to get the "CJ"
stuff. Lubrication Engineers will send you a 5-gal bucket cheaper than you can get
"CJ" oil if you can find it. Theirs is better base oil and better additives.

79jasper · Sep 5, 2017

Maybe I missed it, but I didn't see him say he's changing the oil and leaving the filter.
He's doing fuel filter every 3rd oil change.

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