ISX 5.3 mpg is it normal??

Old site but wanted to see how the air cell is doing, and other ideas how I can get above 6.0 mpg.
ISX 15 485 10 speed 3.55 rears, 24.5 shoes, pull grain trailers, 78, 980K avg wt daily.
Just had all erg system pressure checked, ok.
Does appear I gain about .5 gallon when I use Howes.
Thinking about and erg delete?

 

Wow this in 2008 I got a 2006 isx 550 18 speed did the motor and the rear you name everything was Done by the dealer I haul refeer westcost I am only getting 5.1to 5.0 it is increased from 550 to 650hp I love the truck but it starting to poss me off with fuel when you spend close to 78000$ on it anyone with any suggestions please email me at esanexpress @Gmail. Com

 

Should be getting at least 6.0. I pull hopper and tanker, tanker gets avg 6.3, hopper about 5.6. little better if I keep filter spotless. ISX not know for go fuel. Keep mine at a happy 1400 and she get better mpg.
I have 3.55 rears, with a 10, needs a 13 for Kansas rolling hills.
You can buy an after market air system that spins the inlet air for better combustion.

 

Hello everyone, I have a 2009 Prostar with a ISX 15 750K on it, and I get really bad fuel mileage. I've got constantly about 4.8 MPG no matter what I do. Recently I upgraded to 600 HP settings on the ECM and I've got really nice power but the millage is the same. Boost is good up to 38, cleaned all sensors, recently changed the fuel pump, DPF is new, I do not know what else to do with it. Please help.

 

What tires, flattop, rears, tranny?

I have 24.5, 3.55 rears, 10 speed, best I get with tanker was 6.2. With pneumatic, flattop, 5.3, could get a little better with a 13 speed and watching how I put my foot in throttle.

 

Well I'm no expert but I had an 05 w900 with a 475 isx that was governed at 68 mph with a tri pak...truck was new not wore out .
Very little idle time and it never got out of the high 5s for quarterly fuel mileage.

 

I could also use your help guys ive got a 2010 isx thats been deleted and im only getting between 4.5-5.5 mpg

 

What is your average gross, where do you normally run, and how fast do you normally go?

 

With 5.5mpg at 55000 gross and 4.5mpg and at 78000 gross last run was georgia to indiana grossed at just under 60000lb gross dry van running no faster than 65

 

What RPM are you running at 65 mph?

Seems goofy that you should get that low of mpg. I can run around 70,000 plus and get at least 7 mpg minimum most any time unless I am fighting a tough wind. There could be any number of things that could be a problem. All one can do is use a process of elimination to figure out things.

This may not be any problem, but in keeping with eliminating any possibilities, have you done a recent used oil sample at you latest oil change and see if you have a higher than normal fuel dilution? That would show a bad injector and could explain high fuel consumption.

Don't get all caught up in worrying what might be the cause. Just focus on eliminating any possibilities. I have not been in a truck since the mid 90's that couldn't average 7 mpg. I have been lucky in that regard I guess. Kenworth's, International's, Freightliner's. N-14's, ISX's, and Series 60's. Any truck that can only get 5 mpg in the summertime with 70,000 gross at 65 mph has something going on with it.