NO GAIN IN FUEL MILAGE

[Starrider04]

I have a 04 duramax with the LLY, all stock. I have been getting between 15 and 16 mpg hand calculated. I bought a new predator hoping I would gain 2 or 3 mpg, but after two tank fulls still getting around 16. I drive 45 miles one way to work daily running between 60 and 65 mostly highway. I installed the economy tune 65 hp. Should I try another tune or send it back because the fuel milage is way I bought the predator.

[johan]

Thats odd, when was the last time you changed your fuel filter? I recommend changing it every other oil change as it get dirty pretty quick.
You could also try the 85hp tune but cruising it prolly wont get you any better mpg than the 65 tune, the higher hp tunes help in stop and go driving due to the fact that you do not need to give it much throttle at all to get somewhere.

[Starrider04]

I replaced the fuel filter because I do not know when it was change since I have only had the truck a couple of months. But I don't see how this will affect the fuel milage. I will check it the next couple of tanks.

[Trotorx2]

I expected to see a mpg increase too but it never happened. I have tried all the tunes and hand calculated it is still getting 17mpg. Now...the DIC on the other hand reads as much as 26mpg. Also when I fill up the DIC will report using approx 2 less gallons used than what the pump reads. I have adjusted the speedo and the MPH and Miles driven are correct according to my GPS.

Love the power of the Predator but really wanted the increase in MPG.

[woody]

Hey Trotorx2, same here. I have the 7185. Love the performance but not much on the MPG. With fuel pushing around $4.00. I have tried alll tunes but stock tune is about the best on mpg by about .25. This is on a 05 LLY. I'm thinking of putting on a new exhaust to see if that helps. Good luck. I wish my girlfriend's Prius could pull a fifth wheel.

[mikel]

I expected to see a mpg increase too but it never happened. I have tried all the tunes and hand calculated it is still getting 17mpg. Now...the DIC on the other hand reads as much as 26mpg. Also when I fill up the DIC will report using approx 2 less gallons used than what the pump reads. I have adjusted the speedo and the MPH and Miles driven are correct according to my GPS.

Love the power of the Predator but really wanted the increase in MPG.

Is this with the 65 hp economy tune installed?

[Trotorx2]

I have tried all the tunes with the 7186 and didn't see any increase in hand calculated mpg. I change my fuel filter when the DIC says to and usually get my fuel from the same station.

[clayton74]

I picked up 1.5 MPG with a cold air intake and 4" turbo back straight pipe. Plan to install my tunes soon and will report back.

[Starrider04]

Changed fuel filter just like you asked and only gained about .5 mpg. I am now getting 17 would like to get aleast 19.

[Machoosh]

Changed fuel filter just like you asked and only gained about .5 mpg. I am now getting 17 would like to get aleast 19.

.5 ...... you noticed a .5 mpg increase , good lord , a cross wind could offset that or maybe a colder day or your engine wasn't warmed up.

I can't understand how people stare at there fuel gauge with a microscope, these trucks are all similiar in mileage but can be improved with airbox and exhaust upgrading or modifying ... .5 mpg ... sure it wasn't .6 mpg ?

Sorry I had to vent.

[Skoryaro]

In the last 71K miles I've tried the 40 and 65 HP settings and never see an improvement in MPH over stock.

[chrisshipley]

Hey guys this was the best 300 dollars I ever spent except for the predator. I was only getting 19 mpg onn my 06 gmc sierra 2500hd short bed with 4 wheel drive using the 120 tune. I installed the BD exhaust manifold 3 months ago and now I'm getting 23 mpg. Maybe you should try it on your vehicles.

[jrannis]

Pardon my ignorance but what is a BD exhaust manifold?

[tntm7le]

I have been playin with several tuners and digging hard to get my truck with its tiny little fuel tank to pass through a state without buying fuel.

Every weekend I drive the same 380 mile trip one way.
Have tried all the tunes and the Tow tune has always given me the best overall fuel milage.
Stack that with trans reprogram and I have gone from 14.8mpg hwy to 19's
my city went from 12.2 to 15.7.
My finding is the trany upshifts to slow under light throttle and down shifts to fast when you let off, the truck doesnt coast for crap until your over 50mph, stock the converter will not lock up until 50mph in 5th gear.
I have mine locking up in second gear under light throttle and the motor rpm is way down now and my fuel milage keeps getting better and better.
only have 5k miles on the truck know, But its only 6 weeks old.
My only gripe about the Diablo is you cant do crapola to the trans program.
Only software or tuner that I have found so far that does is EFI live, But its no plug and play programmer.
I am trying now to do a PDF bypass, so I can run the DPF in the city and bypass it on the road, Electric on the fly bypass. My issues are CEL's right now but havent given up yet.
I will have to find a way to keep the backpressure steady so the two sensors give and it doesnt think the dpf needs regen or has a problem.
Then there is the other problem, the soot in the pipe that builds on the back side of the dpf likes to burn when you regen, Can we say Fire hazard!

[Randy_the_Hack]

Well, I went up to 22.4 mpg (best ever) with my Predator (version 2.0) on +65 hp economy tune. I've towed my TT several times with the +40 hp tune. I put on a 4" turbo back exhaust about a month ago and switched over to the +85 hp tune yesterday after a buddy told me his best mpg was on that tune.

Before the Predator, my best mpg was high 16's, low 17's. But I did also add a CAI... but that only accounted for 1-2 mpg.