Fuel mileage dropped about 3-4 mpg,smell diesel fumes a lot,smokes at idle at high altitude,Albuquerque,NM.Took it in to the dealer this am,got a call awhile ago,dirty injectors,leaking head gasket.They say around $4500 to fix everything!:(I haven't been back to dealer yet,just wanting to hear a few responses to my problems and the expense.What should i look for in there report etc?First issue i have had with this truck in 188,000mi,so it's not to bad a record i just don't have a lot to spend on it now that i am retired.Thanks.

Sounds like bad injectors. Make sure they run the balance rates etc.... and give you the numbers, but it sounds for sure like injectors are going out. Also, as far as the head gasket goes, look inside the expansion tank and see if you can detect any soot, and feel the upper radiator hose after it has been sitting awhile to see if it is hard. That more than likely indicates Head Gasket issues. I am replacing my injectors this week. Two were bad but replacing all of them. Good Luck.
DT

Do a search on head gaskets you will find alot of good info to see if its your head gaskets. And if its the injectors they are on waranty for 7years or 200,000 miles so hopefully your not past the 7 years

From what the service writer told me,the injectors didn't fail the high fuel return test,according to the service bulletin the high fuel return test is the only test they use to determine if injectors are bad,is this correct?What should those numbers be,to pass and to fail?I checked my oil last night and i didn't notice any water in oil like they claim.I have noticed my overflow tank got pretty dark and dingy.Will another dealer run another diagnostic on it since i just had it done?I plan on asking for the test results for my truck.Any thing else i am missing?

From what the service writer told me,the injectors didn't fail the high fuel return test,according to the service bulletin the high fuel return test is the only test they use to determine if injectors are bad,is this correct?What should those numbers be,to pass and to fail?I checked my oil last night and i didn't notice any water in oil like they claim.I have noticed my overflow tank got pretty dark and dingy.Will another dealer run another diagnostic on it since i just had it done?I plan on asking for the test results for my truck.Any thing else i am missing?

Correct. The policy only covers failed injectors with high return rates and/or fuel leaking into the crankcase.