Cause of Fuel Mileage Loss?

First and foremost...........your fuel mileage compared to the previous owners fuel mileage is a waste of time unless you're doing the same work the previous owner was doing. If he hauled light loads on flat ground and you haul heavy loads on hill terrian than yur mileage will be much lower. The type of trailer he pulled versus what you're pulling could hurt fuel mileage.

The aftercooler is within spec and isn't causing a fuel mileage loss. you also need to check all the hoses and tubes between the turbos and precooler. You could have a leaking bellows or clamp on these parts also that testing the aftercooler won't show.

 

i would think that anything with a leak should be fixed.

but i would also think that if there were a problem with the turbo system somewhere. you'd be smoking out the exhuast.

since the op didn't mention any smoke.

i would also think that with weak fuel pressure. you would run into a lean misfiring condition.

the op didn't mention anything about running rough.

but i'd like to hear when and if the op figures it out. cuz i just had the turbo rebuilt. egr, actuator and cac all tested good.

my mileage didn't improve one bit from having a bad turbo. i've got more power. and i'm not smoking anymore. and my transmission is working TONS better for whatever effect the turbo was having. but i'm still in the 4.5 range.

 

05w9 isx450 3:55 22.5

started out at 6.2 and i dont' think the turbo was working all that great to begin with. 9 months later with smoke signals. it started with winter blend and just got lower. now turbo is rebuilt and high flow muffler and i gained maybe close to .5. but i'm still nowhere near the 5 mark let along getting back to at least 6

when the mileage got to 4. i used liquid muscle and that brought it to 4.5. been that way for 3 months. doesn't seem to be doing anything now.

course, we'll see what actually happens as my load goes to seattle where i won't have to idle. but i'm not having high hopes

 

Mark- I dont know what boost the c13 runs but pump up ata to that boost level or touch higher to account for boost drop across cooler and check for leaks at that level not at just 20psi....also I have put that 500/1750 euro file in a few trucks...it does well for what it is...not a powerhouse but helped mileage....be glad to give you reference if you holler at me.

 

fs1023 btw

 

You expect fuel mileage pulling a double drop?

Weight doesn't have much to do with it when your hauling double drop trailers and freight. Double drop freight always catches the wind, this is your biggest factor in fuel mileage. If you had a 80,000 pound load that was the size of a gold cart nice and low in the belly, it's easy to keep it moving once your up to speed. With a load that catches wind, your engine is fighting the entire trip to overcome the wind resistance every single second your moving down the road, even if the load is light weight. The fuel mileage your getting sounds a little low, but not terribly off pulling a double drop trailer.

Also, if you want to save fuel, run at 60 MPH, not 65 MPH. In some situations you can lose up to 0.5 MPG, all for what, to get 5 minutes further down the road each hour? Waste of fuel and nothing else.

 

here's what i discovered today.

filled up in phoenix. then filled up at the truckstop where our shop is. all they sell is bio. and it's the cheapest price in the western region.

187.4 gallons divide by 859 miles. 4.58 mpg

stopped in boise to top off for the trip to seattle and back.

38.7 gallons divide by 255 miles. 6.58-------------------------------io've never had above 5.5 before. but the turbo was slowly failing. it was fixed last week.

i'm at 325 miles now and gauge is below 3/4 like it usually. at the 255 mark where i topped off. it was still reading close to full.

i usually get better mileage when filling at the shop truckstop. and now that the turbo is fixed. THAT'S A BIG DIFFERENCE.
but i'll be keeping a closer eye when i fill up there.

the motorcycles of the 80"s used to ALL get 60 mpg or better. with a 55 speed limit and no windshields
today, we're lucky if we get a model that can crack 45mpg. with a 65 speed limit and windshield. for the most part.



i have a conspiracy theory. no facts to prove. just a theory.
since todays trucks are starting to get beter mileage. the quality of fuel is going down. to keep us all getting lousy mileage so that the money keeps flowing in there coffers.

last year i started in this truck with an average of 6.2. it dropped to 4. rebuilt turbo and high flow muffler. i'm still struggling at 4.5. and the truck runs like a grape ape now.

 

Replace that leaking CAC and it is time for some new fuel lines that in my opinion will get you better fuel mileage.

I believe there has already been several post saying the samething.