I have a '99 F-350 dually, 4.10 rear, 4x2, that 3 years old to us. It has a Diablo sports chip in it that is not self programmable. Owner said it was tuned for towing and the chip is so old that Diablo can't tell me anything about it. I get 16 mpg unloaded on the highway and about 12 loaded/towing 7,000 lbs TT. I've seen people claim 23 mpg highway and 17 towing with the same truck, but with different tuners. Can this truck really get much better mileage with a different chip or are people using special math?

Those people are either liars, or they don't realize they being fooled. Hand calculating the mpg would bring them a dose of reality.

Ah, you are getting about the best available with that engine.

Had the 7.3 for nearly 16 years ( early 99 super duty ) 10-12 towing ,maybe 18 on a good day empty highway. Had a DP tuner did not matter what tune it got the same mileage . Had a Superchip before that still about the same mileage. You are about right on with the mileage you are getting, the highway could be a little better, but the only way I could get 17-18 was to keep a little lighter foot on the pedal, and keep it under 2000 RPM's .

My '02 7.3L with 3.73 rear end does about 20 mpg towing with the diesel fuel additive I use, without it about 17mpg. Towing I get abt. 13mpg using the additive. :)

Hello twain,I have a similar truck (early '99 CCLB DRW with 4.10) except that mine is a 4x4. I believe that mine is completely stock and I am getting about 15 in mostly highway driving unloaded. Have not used it for towing yet so don't have those numbers. I am curious to see what real world responses you get but I concur that the those reporting numbers in the 20's are probably not real.Terry

Ford 7.3 chipped mileage | Good Sam Community

mike_brez
Explorer
Oct 18, 2014
Got smoke :E
Bamaman11
Explorer
Oct 17, 2014
I bought my F250 2wd crew cab 7.3 new, and on the open highway it would get about 18 mpg.

I added a 80 hp econo mode chip from DP Tuner, and it went to 20 mpg on the open highway (normal speeds.) I've had not one problem in 10 years' usage.

The problem is keeping your foot out of the throttle, and running it under 70 mph. Most owners don't have the self control to baby the pedal.

My truck would just chirp a tire from a stop. Now, I can burn the tires from a stop. It's almost dangerous to drive in the rain or snow, as it's got so much power from a stop. And 60-80 mph comes up in 4 seconds flat--strong passing gear.

See DieselStop.com if you have any questions about this fine engine/transmission combination.
carl2591
Explorer III
Oct 17, 2014
ib516 wrote:
carl2591 wrote:
i hear you on mods done.. was going on what other had posted at riffraff diesel for one.

the fuel and oil x-overs are more to quiet and excite the engine and driver and can provide a bit of MPG depending on driver.

the tstat i see u are correct at 203 but what is 2 degrees among friends.. :)

I have looked at the 6137? filter deal. was thinking about putting some hole in shroud behind grill to allow more air into the intake pickup area. was wondering how that might work with rain.

I was going to keep the holes maybe 1" round just below the lower part of air intake mouth you see in pictures.

I have several pictures of what i was seeing and had marked the shroud to show where the grill bars are located. I will post them here.

( not shure how this works here)

LINK TO PICTURE

thanks for that.. :)
ib516
Explorer II
Oct 17, 2014
carl2591 wrote:
i hear you on mods done.. was going on what other had posted at riffraff diesel for one.

the fuel and oil x-overs are more to quiet and excite the engine and driver and can provide a bit of MPG depending on driver.

the tstat i see u are correct at 203 but what is 2 degrees among friends.. :)

I have looked at the 6137? filter deal. was thinking about putting some hole in shroud behind grill to allow more air into the intake pickup area. was wondering how that might work with rain.

I was going to keep the holes maybe 1" round just below the lower part of air intake mouth you see in pictures.

I have several pictures of what i was seeing and had marked the shroud to show where the grill bars are located. I will post them here.

( not shure how this works here)

LINK TO PICTURE
carl2591
Explorer III
Oct 17, 2014
i hear you on mods done.. was going on what other had posted at riffraff diesel for one.

the fuel and oil x-overs are more to quiet and excite the engine and driver and can provide a bit of MPG depending on driver.

the tstat i see u are correct at 203 but what is 2 degrees among friends.. :)

I have looked at the 6137? filter deal. was thinking about putting some hole in shroud behind grill to allow more air into the intake pickup area. was wondering how that might work with rain.

I was going to keep the holes maybe 1" round just below the lower part of air intake mouth you see in pictures.

>>>>

I have several pictures of what i was seeing and had marked the shroud to show where the grill bars are located. I will post them here.

( not shure how this works here) man that was hard..

you see the two holes below the xxx out area was where i was look to make my 2- 1" holes beside each other.. the out door sensor was in one of the holes.

you can see them larger by clicking on each picture or pasting in browser.

[url
http://absolutebestcarpetcare.com/abcc/wp-content/uploads/2014/10/IMG_1699.jpg]LINK TO PICTURE 1
[url
http://absolutebestcarpetcare.com/abcc/wp-content/uploads/2014/10/IMG_1700.jpg]LINK TO PICTURE 2
[url
http://absolutebestcarpetcare.com/abcc/wp-content/uploads/2014/10/IMG_1701.jpg]LINK TO PICTURE 2
[url
http://absolutebestcarpetcare.com/abcc/wp-content/uploads/2014/10/IMG_1702.jpg]LINK TO PICTURE 4

i give up....
Twain
Explorer
Oct 17, 2014
No onboard calculator on the 99 XLT. My 12 towing 16 highway is cruising at 60 MPH. 4.10s start to hurt much past that. Thanks for the info. I'll probably keep the engine as is. The tranny shifts hard, real hard and I suspect its from the Diablo chip tune. Have the brand chip in a 96 mustang and it did increase line pressure.
majorgator
Explorer
Oct 17, 2014
carl2591 wrote:
I have a 2003 7.3L PS with 168K miles that i just got 2 months ago. The truck is stock.

In some of my reading on http://www.powerstrokenation.com/ or http://www.ford-trucks.com/forums/forum31/ you can see where the motor which is an International made diesel was detuned by ford.

Some of the stuff that stunts the MPG is they (ford) redesigned the water pump and use a 195 instead of the original 205 deg stat.. Diesels like to run hotter. You can see post of guys changing out t-stats and waterpumps getting some 1-2 MPG increase on that alone.

The 6 position tuners also give some 1-2 MPG on the 75HP setting as well..
As far as engines go this is maybe one of the most reliable ones made.

there are fuel crossover hoses kits that help with injector noise and can help get a .5-2 MPG same with High pressure oil cross over lines on the engine.

I choose to buy an older used model to do some mild mods on over a period of time till we get ready to go full time in 4-5 yrs.

I think buying a new truck is nice but i would rather let someone else take the desperation hit and get one from the original owner with 80K or so miles for 25 to 30K less than new with a diesel engine.

Gas is good but for towing diesel is KING..

peace out. :D

Take it from someone who's done all the mods you speak of (except fuel crossover), all those things together didn't really do squat for my mileage. But my truck does run and perform better, which was/is the main purpose. Check on your t-stat numbers, though. I have a DieselSite 203 deg thermostat, which I believe is the one they say to be the original spec'd one from International.

Now that you have this truck, time to open it up and let it free. Tymar (6637) intake, tony wildman tunes, stage 1 injectors, 5" exhaust...you're gonna be able to get so much out of it!!
majorgator
Explorer
Oct 17, 2014
Hybridhunter wrote:
Funny how the great mileage numbers come from guys who driver "average speeds". How about posting your highway cruise speed and let us judge what is average. No way anyone with a 7.3 is getting 20 mpg at 70mph, or 65 for that matter.....

Well, it depends on your definition of highway cruise speed. There's a huge difference between 65 mph and 70 mph on these trucks in terms of RPMs. For me, 65 mph is a shade over 2k RPMs. The best I've ever done is a little over 17 mpg. My truck is big, heavy, has 4:10's, large injectors, oversized tires, and MANY mods. 20 mpg with a smaller 7.3L truck, properly tuned and not venturing much over 65 mph is a very reasonable number. Spend a few minutes online and you'll find it to be very common. And yes, these are hand-calculated figures since many of these trucks don't have an onboard computer doing the figuring.
mec500
Explorer
Oct 16, 2014
I have a 2002 7.3 with a DP TUNER set on 60 hp mountains. In perfect running condition with a ford ais intake and open exhaust and I get 16-17 mpg unloaded running 70 mph at 2100 rpm. With the toyhauler @14k fifth wheel and as aerodynamic and a brick I get 8-9 mpg @ 2400 rpm
The boat @5k is around 11-12 mpg @70 mph .the mpg would be much better if I kept the rpms under 2000 but. With out the chip is the same. I do not believe for one minute anyone is getting 30. I have know one person in the Real world to get 20 and this was a two wheel drive single cab with highway tires and manual trans .
Hybridhunter
Explorer
Oct 16, 2014
Funny how the great mileage numbers come from guys who driver "average speeds". How about posting your highway cruise speed and let us judge what is average. No way anyone with a 7.3 is getting 20 mpg at 70mph, or 65 for that matter.....