My Truck has 169,000 on it and has started idling real bad when I first start it up, after it warms up it gets better, this morning it looked it blew out a little blue smoke when I left the house, I pulled over and let it warm up and did alright the rest of the day. Mileage is down about 1 to 2 miles a gallon. Anybody know what I might need to look at? Thanks for any help.

maybe the fuel filters, air filter. i know desiels need lots of air flow.

they need even more fuel flow!
You might get a Dodge guru to check out your truck. It almost sounds like a bad lift pump or injection pump to me.

5.9 or 6.7?

either way, sounds like an injector or a pump

5.9 I am thinking injector problem

Did you let the grid heater run until the light on the dash went off?

If it gets cold you need to turn the ignition on and wait till the red light on the dash goes off before you start it.

Thats the simpleton thing that it could be. I know its been colder here the last couple of days. Thought I'd rule out the simple stuff first.

The last 2 days I have been waiting till the engine warms up and it runs better but still idles rough, I wait for the light to go out before I start it.

Whens the last time you changed your fuel filter? Also I believe during the winter there are additives in the diesel that have to do with the drop in mileage. But an old fuel filter can also cause the drop in mileage. Also you have to remember that all the times the truck is sitting warming up its burning fuel so if it sits for 15-20 min every morning warming up in the driveway that can also show up as a mileage drop.

I could be an issues with an injector too I suppose but I dont think it would go away when the truck warmed up. Are you noticing any loss of oil?

I didnt see it but how long have you owned this truck?

Bought it new,new fuel filter at about 110,000, not using any oil,mileage drop before I started letting it warm up.

any white or blue smoke under a load?

Blue smoke if I do not let it warm up

If it were mine the first thing id do is change that fuel filter. Its easy to get too and with 50-60,000 on it its past ready to be changed.

Do you have any leaking around the head gasket or have you been losing any oil or coolant?

Changing filter in the morning,no oil or coolant leaks.

you really need to change that filter a little more often,i would change every 20-25k miles,also you can add some diesel kleen to it from time to time to keep everything lubed and cleaned properly.

when you change your filter, prime it with some ATF, then pour a quart in your tank and see if it clears it up...