mpg really starting to suck

[papavillars]

hey guys I have a 2006 duramax with 80,000 miles. all of a sudden the mileage went from 18.5/19 mpg to 15 mpg. all fluids changed on schedule any thoughts, or how about a chip.

 

[Red Bull Breeder]

Get used to it may get worse.

 

[JHH]

Does it smoke blue alot while idling? May need some injectors,or it may be that you are just letting it idle longer because it is cold out.

 

[highgrit]

Is it the early model engine LLY or the later LBZ. Had the catalytic converter plug up on the LBZ, lost power and MPG.

 

[LRTX1]

I had a 1/2 ton chevy once, after I got new tires my mpg dropped by 3. Come to find out the tire guy only put 28 lbs in them. I set them back to 36lbs and mpg returned close to normal. Not saying thats your problem at all but tire pressure does afect mpg's a lot.

 

[Thinbluelinetx]

Does your truck have a diesel particulate filter? If so, it will occasionally go into re-gen mode and use more fuel to burn up the crud in the filter.

 

[JHH]

Does your truck have a diesel particulate filter? If so, it will occasionally go into re-gen mode and use more fuel to burn up the crud in the filter.

I dont think they had those till late 2007 or 8 but I may be wrong. That does happen alot.

Is it the early model engine LLY or the later LBZ. Had the catalytic converter plug up on the LBZ, lost power and MPG.

The 06 should have the LLY. I am wrong on the injectors also i think. They didnt have much trouble with the LLY injectors.

Might check tire psi like LRTX1 said that does make a difference

 

[papavillars]

I do have the LLY. I will check the tires. Regular filter, but it is probably time to replace it. $ 3.19 a gallon sure aint right. Sure wish i could run it off my gas wells.

 

[highgrit]

In 2006 GM put 2 different duramax diesels in their trucks. One being the LLY, the eighth digit on the vin # will be a 3, and the eighth digit on the LBZ will be a D. If your going to state facts, you need to know the facts.

 

[terra8186]

My business owns a few of these trucks. Most of the time it is an injector problem. Look for excessive smoke out the back (like JHH stated). I had one drop so much out the back, the trailer was covered in diesel. Very common problem for us.

 

[Tod Dague]

I have a Cummings and had a similar situation a year ago. My fuel mileage dropped and I started blowing a lot of black smoke when I towed a load. Turned out that I had blown off the air line between the Turbo and the air cooler. I hope yours is just as simple.

 

[ga.prime]

You think it sucks now. Wait'll fuel gets to $5/gallon.

 

[High Cotton]

When was the last time you changed the fuel filter?

 

[gimpyrancher]

I have an '07 duramax (Classic) long box crew cab (165,000) and on a good day I can get 16 on the road at 70 mph. Towing weight or having a tall obstacle in the bed I get down to 14. No smoke.

 

[tytower]

I would put an each way bet on the injectors also. What often happens with diesels is they get tired and like old men start to dribble the fuel out rather than atomise it like teenagers. So, is it hard to start when cold? When the motor is hot you won't notice much difference except consumption.

The fix for this is new needles and seats and is usually only $100 per cylinder or so plus labour . The injector is pulled apart and a new needle and seat fitted.Its a quick job.

Another consideration is friction at the wheels , like a sticking hand brake or disks not able to turn freely. Check the hand temperature of each wheel hub after say 10 minutes of travel. A sticking one will be hot and binding.

Tyre pressure too but not so much unless they are really flat. See the tyre placard on the drivers door, or the manual for the right setting . If you have recently put a large tradesmans toolbox in the back it might feel like a 1/2 ton of cement bags.