Poor fuel mileage

check your odometer for accuracy. it might be spinning slower then it should. i've driven trucks that will rack up 1050 miles on a 909 mile gps trip. and i've driven trucks that will only rack up 850 miles or lower. on the same trip.

i also use liquid muscle to clean the injectors. when my mileage goes down. that stuff gets it right back. i use the stuff about once a month. but we run a lot of bio fuel. one bottle will treat 750 gallons. and only cost $20.

your ecm might need looked at. for problem sensors. or maybe it needs to be reflashed. it's running the injectors pulse width too long.

air filter and tire pressure look good?

what brand oil are you using. maybe switch brands. my last company uses a brand. that literally costs me power and .5 mpg less. makes the motor run hot. and sounds like a time bomb waiting to explode. but if i use mobil 1. the truck purred like a kitten. with better power and fuel mileage. and cooler temps.

you said the turbo was fine. was it checked for full rpm operation???? how about the charge air cooler??? the holset turbos on isx motors spin at 45,000 revolutions. when working properly.

it's also winter time. poorer quality fuel.

and for the big question. how much are you idling?

those are the things that improved my mileage.

others will come along with other solutions for you.

 

Leaking charge air cooler is a possibility. But as stated numerous things can cause poor fuel economy especially this time of year.

Do you own your own trailer?

 

Like Snowwy said there are a lot of reasons why the fuel mileage has changed. Only thing I could add is have you changed your tires recently or checked air pressures?

 

what are you pulling? i have a volvo my average consumption is 2.83 m/g converted from metric (Aus) with signature cummings 630hp but this economy rate can fluctuate buy upto 50% dependant on what im towing Single Double or Triple roat train but oter things like type of trailer even with the same payload can affect fuel use i also reduced fuel use with a full aero kit on the truck without a aero kit it was like pulling a brick wall through the wind (my volvo is a cab over) and even the position of turntable (5th wheel) and the gap between cab and trailer can affect it. fuel use can also be reduced with driver technique a simple one is less flat stick & high revs to get up to speed same as a gradual reduction in speed instead of stoping with the brakes all the time the less time with the pedal on the floor the better. I also found that cruise control can affect it for example if you drive without cruise you will change down gears before the engine is labouring at low revs in top cog using more fuel. The 6.5 your hoping for may also have been calculated in totaly different operating conditions than the purpose you operate.

this might help a little im sure there are others with more technical answers for you but with our fuel price being $5.80 per gallon AUD over here fuel consumption is something we try to keep down as best we can.

 

Aussies call 5th wheel's turntables ? I like that !

 

No,Danny,Aussie's put a turntable under the fithwheel.
Mostly those who run roadtrains.(so i have been told)
Has to do with the work conditions.

 

It's a table that the trailer sits on and it turns hence "turn table" haha different terminology it a good laughter sometimes. Does calling it a fifth wheel mean that on a bogie drive truck it would be the 7th wheel haha.