Okay, I have searched and read all the threads on fuel mileage for the CTD's till I'm damned near blind, but would like to know what's the best gears to get with auto trans, 4x4, 2500 to be used mainly for an almost daily driver and pulling a 6-7000 lb trailer 6-8 times a year?
Also, how long and how much of a "break in" to get the best mileage? Do I need to start with the "additives" right away or wait a while? I'm considering a 06 2500 Mega Cab 5.9 CTD I'm old enough that this will probably be my last truck buy.Thanks in advance.

 

With that light towing 3.73's are good. If you start towing after about 500 miles, the rings will seat quicker than if you don't work it.
I have roughly the same average tow, and it still getting better and better after 34000. It seemed to plane out mileage wise at 20000 or so and now is increasing mileage ever so slightly. Cummins does not recommend additives unless you need anti gel for COLD weather. Many would argue that, and they run Power Service, TCW-3, Marvel Mystery Oil, Stanadyne...and several others every tank. The additive question is very loaded and usually becomes a passionate debate on any of the forums. I run Power Service every third or fourth tank to give the injectors a bit of a wash, and Marvel Mystery Oil (MMO) most tanks to give the fuel system a little extra lube. These are just my routines, and there are a lot of others who run other chemicals.
Welcome to our oil burning world....Enjoy!!

Cheers
Mike

 

I have a 2005 CTD (first ever diesel), auto, and 3:73 gears. Even pulling 12 to 14,000 at 70 to 75 mph, the engine seldom works hard enough to drop out of overdrive unless the hill is substantial. I like quiet and with the engine loafing along at about 2100 rpm, the cab is very quiet.
It's overkill, but I changed oil and filter the first time at around 1200 miles. Later, I'll probably go 7,000. No additives used.
Hope you enjoy.

 

I have an 05 with 1700 on the clock.
Iv got the 3.73 gears and am pleased with the truck.
As for a break in, about 500 miles as was previously stated should work fine.
As for additives, personally I use 8 oz Marvel Mystry oil and 16 oz Power Service in the white bottleper tank ful.
Hope this helps.

 

I also have an '05 with 15k on it (bought it used), I use the 16 oz of PS & 8 oz of the MMO each tank. I found it consistently gives me an extra 1.5 mpg. went from 15.9 to 17.5. Last Friday I added an AFE Stage 2 CAI and milage looks like it's jumped up to 19, either that or the diesel in NV is some killer stuff (or like CA gas, CA diesel sucks).

I use mine as a daily driver so it gets alot of city/hiway mixed.

 

NV5600 (6spd) and 4.10's[sm=badbadbad.gif]

this combination is terrable on fuel mileage sincec at 70mph I'm turning 2300rpm. if I had 3.73's I'd be running around 1900-2000. If I bought my truck all over again I would probably get the 3.73's since I dont tow much. but now that I have it I wouldnt trade it in knowing I can pull anything I hook up to