I sold my 96 7.3 after 18 years that got 20+ hwy/17+ city mpg and picked up a 2000 7.3. The best mileage I was getting with the 2000 was 16.8 hwy. I started reading as many posts on as many sites I could find to improve mileage. After reading the most common advice given I did the following mods ... 4" AFE SS exhaust, no muffler, Donaldson air filter kit from Riff Raff, and a DP Tuner, Jody recommended (for better mileage) the chip he sent is 1. Stock, 2. 60hp, 3. 80hp ... since doing the mods I've gone from 16.8 to a best of 13.3 mpg ... FYI- the advice I read also said keep at or under 2000 RPM's ... I've been driving like a blind granny since the mods .....

Truck - 2000 f250 7.3, ex cab, 3:73 axles, Auto transmission.

Anybody know what I can do (or undo) to remedy this?

 

I guess to ask the obvious first, you are running in "stock" with your tuner?

I have about the same truck and run only completely stock and my truck gets about the same as your first truck did without mods on a good day. Kind of the first rule of modding from what I see on FTE is first make sure everything is 100% in stock trim before adding mods. Do you have gauges or anything else to tell you what is going on with your engine i.e. Forscan, Torque Pro, etc. ?

Steve

 

Steve, Jody at DP Tuners initially asked what mods I was going to do, then came up with the chip/what ever it's called. He said to use the #2 60hp position for towing and use the #3 80hp position for everyday driving. One of the tech guys I talked with after I installed the tuner and discoved the loss of mpg said use the 60hp for everyday driving. The only thing I tow is a boat that with trailer weighs less than 2700 lbs. All flat driving at less than 500' above sea level. Jody said because of what I'm doing with my truck, gages really aren't necessary. He also told me when I questioned him about losing 3+ mpg to put the stock Ford air filter assembly and the original 3-1/2" down tube back on because the 4" down tube doesn't let the turbo spin up quick enough. To my uneducated mind, that sounds bass ackwards.

If I was originally looking for performance I'd happy but that wasn't the case, my motivation was MPG ... when I want performance I go to the lake.

 

First of all, run it in stock mod and see what you mileage is. Until you establish a baseline, you can not even tell what effect your mods had. I am not downing Jody, but you started out with mileage that was off. You should not need mods to get average mileage and in general mods increase mileage very little if at all according to most reports on FTE.

How many miles on your truck?

Steve

 

in Stock MODE and running RIGHT...

MODS... will almost NEVER return better fuel mileage...
reason, more fuel needed for more HP.
second, driver almost never drives a Modded engine LIKE they did when stock....

even lightly dragging brakes will DROP fuel mileage and on a 17 year old truck. .
MANY things will cause a mpg drop.

 

Truck just turned 203,xxx mi. When I run it in #1 stock position it's sluggish feeling compared to stock/no chip. Jody explained that stock/with no chip the motor can or does advance to higher degrees of timing, his program doesn't allow timing to go that high. I really hope I understood his explanation correctly, I'm going to call him again to clarify. When I called Jody to discuss mileage issues, he said others have called with the same lower mpg issues. At this point I'm going to do what Jody recommended to them, he said I should get back to the mpg before the tuner. I'll put the stock air filter assembly back on and check mileage again. If that doesn't help I'll put the stock down tube back on. If that doesn't help, I'm pulling the chip out and hopefully see 16.8 again.

 

SO far you are 100% correct re mods not improving mpg.

Like I said in my original post, I do my absolute best to keep RPM's under 2,000 ... hard to do unless I lift the peddle at 2,000 - 2,200 RPM's. The trans just doesn't seem to want to shift until 2,500 - 2,700 RPM's

After getting 20+ mpg for 18 years in my old 96 all I was after by doing the mods was increasing mpg. Never thought I'd see more than 18 - 18.5 because it's a automatic trans but, going backwards/losing mpg is disappointing, especially after months of reading the "how to increase mileage" articles/threads from multiple 7.3 forums.

 

Couple of thoughts. First, it has been noted multiple times that tunes virtually never increase mileage.

Secondly, doing mileage checks in an uncontrolled environment is extremely difficult and has to be done over multiple trials in order to randomize effects of the multiple variables that come into play.

Finally, with that many miles on the clock, your truck is well broken in and there is plenty of room for things to be worn or simply not working like they should. All those possibilities have to be checked and corrected or mods don't do much.

I do worry you do not have gauges if you are running mods. At the very least, a way to monitor EGTs and tranny temperature are virtual absolutes for 7.3s, if they have been modded and in my opinion, even when they have not if towing or driving in an area with elevation. My truck will run EGTs of 1300 while on cruise control and towing in a heartbeat once it starts to work, if I don't back out of it. Better safe than -

Steve

 

RV_TECH ...

I talked with DP Tech support a while ago, he explained that running on the 60hp towing position was what was causing the higher RPM's before trans would shift. I drove it a bit ago in the 80hp daily driver position, he was right ... the trans shifted into 2nd at 2000, 3rd at 2100 and 4th at 1800 rpm. I'm going run a few tanks of fuel and check mpg .... hoping it'll make a difference.

 

That's a big clue on your previous truck, it was an OBS which are a lot lighter than a Super Suty, and since its winter your filling up with winter blend diesel which will kill mpg.

 

Um .... I was getting 16.8 before mods, now after mods 13+ .... the 16.8 WAS winter diesel