I have been reading up on the Cummins forums because I want to get a truck in the near future. I have friends and family members that have them but I wanted to get a better representation of expected fuel economy.

Going to a diesel...economy is the most important to me. The second is the towing power for a 5000-6000 lb trailer I realistically would be towing over the weekend once a month.

I am pretty set on a 2006 4x4 auto megacab with 3.73 gears, but...will admit that I have been interested in the same year Duramax crew cab.

There are a lot of things that affect economy negatively: the most is driving habits, people not knowing how to calculate and take tire size into consideration, tire size/weight, vehicle height, and auto or manual transmission to name a few.

What I learned on the economy posting is that its all over the board because of at least one of the above effects. Lets just say that I hear the Cummins has the best economy, but I am not so sure when comparing apples with apples at the same HP rating.

From my personal experience my father in laws 2006 quad 4x4 auto (don't know gear ratio) on the average gets 16 city 18 hwy. My friends 2009 quad 4x4 6sp manual gets 18 mpg average (3.73 gears), mostly highway. He had a 2004 same truck with 4.10 gears and 35's that would get 18-20 with the manual tranny. I asked a guy with a 2009 mega 2 wheel drive auto what he was getting...14 city 16 hwy! To me that's not acceptable for a 2-wheel drive, not for me to spend the money. I know they getting better fuel economy with miles, but that isn't a good start to me.

When I get a truck I don't want to be under 16 in the city. Any thoughts besides driving like a granny. I just want to drive normal and get respectable mileage.

Thanks
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OK you named off 3 completely different CTD's that is why you are so far off base.

OK a 2004 has a different Injector pump than a 2004.5 and 35's would change a 4.10 to about 3.80 ratio rear end. Hence the decent MPG on the highway

06 has the same pump as the 04.5 with a CAT under it. It has more HP than a 04. 04=300/555 or 250/450 and 04.5- 06=325/610 and if left stock and driven normally will get 16-18Mpg

Now a 09 is the 6.7 and has tons of emissions stuff on it. And is bringing down the mileage. Also this guy may have the 4.10 rear end.

So best Fuel mileage is a 03-04 H.O or S.O. Then the 04.5 is best for making tons of extra power easiest. But you pay a bit in the MPG and the 09 is the new motor(mostly 5.9 parts) and is hindered by emissions

But there is a trick to getting better MPG on a 09 you have to do a small mod. Its discussed in the 4th gen threads

 

First of all, these are the specs for the years.

2003 S.O. Federal Emissions: 250HP/460lb.ft. Available with NV4500 or 47RE
2003 S.O. Calif. Emissions: 235HP/460lb.ft. Available with NV4500 or 47RE
2003 H.O. Federal Emissions: 305HP/555lb.ft. Only available with NV5600
2003.5 The 47RE was replaced by the 48RE automatic transmission and available with the H.O.

2004 S.O. Calif. Emissions: 235HP/460lb.ft. Available with NV4500 or 48RE
2004 H.O. Federal Emissions: 305HP/555lb.ft. Available with either NV5600 or 48RE

2004.5 (50 state legal) 325HP/600lb.ft. Available with either the 48RE or NV5600

2005 (50 state legal) 325HP/610lb.ft. Available with either the 48RE or NV5600

2005.5 The NV5600 replaced with the G56 6spd manual gearbox.

2007 6.7L Cab and Chassis 305HP/610lb.ft with either the Aisin 6spd Automatic or the G56 6spd manual gearbox

2007.5 (50 state legal) 6.7L 350HP/650lb.ft with new 68RFE automatic and 350HP/610lb.ft with G56

Two exact trucks could have different mileage, however it would be close. The thing you have to know is a lot of people do not calculate mileage correctly or go by the overhead. I don't know how they get it wrong but somes claims are downright impossible. My truck in my sig got 16 MPG city stock, and that was driving moderate. On the highway if you drove the speedlimit it would be about 18 MPG. With current mods i'm sitting at about 14.5 city, and 16 mixed. Some are claiming huge mileage gains with programmers, again a lot of it is you believe it's better mileage then your really getting. I do not believe for one second any truck by adding a programmer will see a 4+ MPG increase. The 6.7 is only like 40% takeover parts, so no it is nowhere near the same as the 5.9.

A 06 megacab auto 16 city is very possible though.

 

Is that true ?

 

Yeah has less TQ

 

Actually it is 305/610 for the G56 trucks. They detune them do to inefficiencies with a manual while doing Torque management. In other words they can't control the TM as well as with an auto.

 

My 06 auto with 3.73 (325hp/610tq) will get 16-17 city and 18-20 highway unloaded bone stock with stock tires. Hand calculated every time. It never has gotten under high 15s even when letting it warm up in the winter for about 5 minutes every morning..

You know its really hard to calculate true city/highway mpg on a truck with a 35 gallon tank unless you purposely fill it up after an all city run or an all highway run.

 

Why do you think he was ****?? He posted to the fact that there are a ton of variations that can affect MPG of the truck. He may have missed the 09 but the OP was talking about getting an 06 and was complaining about the quoted 09 mileage.

 

I was pretty sure the torque increase in an auto was due to the fact that a torque converter is a torque multiplier due to the fluid coupling as seen in this article.....

http://www.tciauto.com/Products/Tech..._explained.pdf

 

If it's any help here is a graph of my fuel log for last year. 2008 Ram Fuel log.pdf . Hand calculated maximum was 19.91 minimum was 13.21 bringing the average for 2008 to 16.59 mpg. The overhead showed 21.2 maximum 15.4 mininum and avg. of 17.9, I reset the overhead every time I fillup. The graph starts in January and ends at December that is why it is higher in the middle. In the middle the few low readings was when I towed the boat. As you can see the mileage is all over but being a daily driver and sometimes all city and sometimes mostly highway. The truck is an 06, automatic, completly stock with a 3.73 rearend and don't drive like grandma .

 

You can't go wrong with a late 5.9L ('06 like you mentioned). My '07, same engine, but 6speed, gets 17mpg around town (but even around town is 10mi ea way on the freeway, no traffic) and 18-19 mpg on the hiway at 80mph+.
Pulling a 4klb ski boat, gets about 14+mpg at 80mph on the hiway.
Almost identical mileage to my '02 DMax.
IMO, you can't go wrong with the LBZ DMax either. I had great luck with my LB7 and they're known for more problems than the LBZ. If you're set on an auto trans and pre DPF trucks, the 6speed Allison is hard to beat.
Either truck will tow your trailer like it isn't there.

 

So I noticed you said a lot about certain things, and I always tell people, be realistic in your choice. Are you buying a 5.9 (or 6.7) 2500, or 3500 cause you want to, or you need to? I noticed you said your trailer is 5-6,000lbs and you tow once a month? Can you wait till the new 1500 diesels come out? if you want good millage that would be the way I would go, they will get better millage, and they will tow that 6,000 lbs just as good.

The 2500's and 3500's (I have a 2500" are great, but remember they will weigh around 2,000lbs more than a 1500, that alone is a millage helper.

Again just tossing out the idea, if I were to buy new for my trailer I most likely would buy a 1500 if it met the needs (I only bought the 2500 for towing, and hauling) not a daily driver. If it was my daily driver, I'd most likely buy a 1500 for sure (better ride, ect) I also didn't buy a quad cab long bed cause I live in the city, I wouldn't fit

Lots will say I get 22, lots say I can't get 15, take everything into effect, most list gear's and trans, but forget to mention, the flats of texas vrs towing through the rockys with 10,000 lbs a day, or 4x4, or 2x4, or weight, or tire size, or what tire pressure they run, or what chips, turbo, sticks they run. I always try to list my mods.

I tow a 20 foot enclosed wells cargo trailer (8 feet wide) It's a brick when it comes to wind resistance. Weighs around 6,000 lbs when I tow. I have a 4x4, 2500, quad cab, long bed. Tires at 70psi, 3.73 gears auto trans, mostly stock stuff. i have a tst I run on 3/2, and I tow at 75mph from RI to Maine (there are lots of elivation changes) not like the rockys but a lot of hills. I get around 13-14 at this speed. slow to 65, and I can do almost 16-17 with the trailer, speed, and engine rpm are a big killer.

Best millage ever was 19.9mpg heading down to VA one year, just what my truck gets (an 05) Again 75mph the whole way empy (well maybe 400lbs in the bed). I've also put on a tonue cover but have not kept up with my log enough lately to track (I have a log of every drop of fuel since new) so I do track everything (from additives, to style, amount, blends) everything. I do try to squeeze the most out of it. This was also on regular diesel, not the premium some seem to get (problably could get 20-21 with that.

There are so many factors in millage, really consider what you do. Going with 4.10's to pull that load wouldn't be good, but if you upgrade to 35's maybe. I have 3.73's and am going to lift it, and think the gearing will be perfect. Right at 2100 rpm you get a drone, and with the 35's I'll be down to around 1800 rpms (which is the torque area). I doubt I'd need 4.10's, I don't haul that much (over 10,000lbs) so I have to down shift..

Good luck and happy hunting

 

My 07 QC 4X4 dually has 3.73 gears,auto, 5.9 CTD, overhead ladder racks & large aluminum topsider boxes, loaded with tools, 14 city, lately in the warmer weather i have gotten 17.5 on the highway, steady 65 cruise, that 17.5 is hand calculated.

 

15 - 16 in 60 city/40 hwy driving. The 5.9 is going to give you the best mileage, and the 06 - early 07's have the best version of the 48re transmission.

 

I average 16.8-17.3mpg Commuting, same commute my wife averages 15.3, driving habits have an effect. Flat commute with one 700' hill, average speed 23mph.

Best seen, 21mpg (Happened one time and it'll probably never happen again)

Worst seen, 15.3mpg (Wife commuting)

Absolute worst seen, 9.3mpg (#3 injector failed open)

I should add...With that light of weight and that little amount of towing, you may be better served with a 1500. Yes a Diesel will get much better FE, but you're paying a lot more upfront for that FE.

The only reason I purchased a 2500 Diesel was because no one in our family had a vehicle that could handle the family's 26' Cabin Cruiser and 19' Trailer.