Buying Used 3rd Gen, What year is best

[mwilson]

After reading all the info in your reply (and those of others), it appears I really goofed in buying an '07.

My mileage is rotten and I am now wondering what options I have;

1. sell it and buy an '05 or

2. can the engine be modified (within reasonable economic limits) to improve mileage or

3. swap in an '05 engine?

My '01 was awesome and gave great mileage, but I wanted a dually to pull a 27 ft 5th wheel trailer, so I sold the '01 and bought this fuel hog '07. Buyer's remorse.

BTW, I have tried a Smarty Jr. and after more than a year of fooling around with settings, it really does not seem to make a whit of difference in my truck, even though others have reported success with their's. I have even tried running this truck with SRW's and if it makes a difference in the economy, the difference is too small to measure.

1) What is your current fuel mileage??



2) What speeds are you running???



3) How many miles are on the truck currently??



Just curious. .



Mike.

 

[Jim Ross]

My mileage running empty rarely goes above 12, maybe 13 rolling downhill with a tail wind.
Pulling an 18 ft box/cargo trailer at 65mph it varies between 8 and 9 mpg; pulling our 27 ft Arctic Fox 5th wheel at 65 mph it is even less, I have gotten as low as 6. 5mpg.
There are approx 44K miles on the truck.

 

[mwilson]

My mileage running empty rarely goes above 12, maybe 13 rolling downhill with a tail wind.

Pulling an 18 ft box/cargo trailer at 65mph it varies between 8 and 9 mpg; pulling our 27 ft Arctic Fox 5th wheel at 65 mph it is even less, I have gotten as low as 6. 5mpg.

There are approx 44K miles on the truck.

Well then, I can't give you the old slow down speech, can I??



I wondered as my '06 will drop it's mileage at speeds over 65mph.



We share the same powertrain and I get 16-17mpg empty at 75mph. I have achieved 20mpg on a few occasions but that was before ultra low sulpher fuel.

It will still get 19mpg if I stay under 70, 68 is really the best speed for making time and stretching the distance between fuel ups.



Towing an 11,000lb fifth wheel will give me between 10-12mpg again depending on speed and headwind.

Towing happy spot is 62mph. Push it just a few mph faster and you can make the 12mpg into 10mpg.



Some trucks take longer than others to break in, mine did not fully free up and come completely alive until the 50,000 mile mark. That is also the point that I began to get the best fuel economy.



Now at 116,000 miles it is an animal.



I am stunned at your poor mileage, has it always been that low????



Mike.

 

[AH64ID]

Mileage seems quite low.

1) speedo/odo accurate?
2) brakes dragging?
3) making oil?
4) good power?

What do your boost/EGT's look like doing 70?

 

[Jim Ross]

I bought the truck used, so I can't say if the mileage has always been so poor, but it has always been this poor for me and I have owned it for approx. 2 years. It had 27K on it when I bought it, it has approx. 44K on it now.
The truck has always seemed to have good power; my '01 was hopped up with 275's, had an Edge EZ chip and a Turbo-Master with 4" straight pipe and I think it was likely in the 300+ HP range, this '07 seems to have more power than the '01 and this truck is stock except for having no muffler.
I have checked the speedo/odo many times against mile markers and, if anything, the odo reads a tiny bit more than the mile posts... . which when calculated would give me a slightly higher mpg than what I am really getting.
It is not making any oil, doesn't leak any and seemingly does not use any.
I do not believe the brakes are dragging, I check wheels/tires for temperature almost every time I stop for fuel or pull into a rest area on the highway. I keep the tires inflated to the max cold psi.

 

[Jim Ross]

Forgot to answer the EGT question. It stays in the 800-900 range at 70 mph and the boost runs pretty high (compared to the old '01)... . usually in the 20's.

 

[AH64ID]

Your EGT's and boost seem a little high for empty highway cruising, but maybe that's just the hips?

In stock trim at 70 I was about 10-15 psi, with 80 being 12-18 psi of boost.

The added boost/EGT's mean the motor is using the fuel to make power, so I wonder why it needs more?

 

[Jim Ross]

Yeah, it has got me frustrated, that's for sure.
I will drive it to Las Vegas and back (from Reno) pulling the 18 ft box trailer (loaded) at the end of January, so I will get another rude awakening at the fuel stops.
I guess I would consider doing the cam and turbo change... . IF I am convinced that I could get the mileage up to 16-17 minimum.
I still have the CAT on it, but I don't think pulling it off will make a difference in economy... maybe in cool-down times... maybe.

 

[AH64ID]

My cat effected cool down times and nothing else.

 

[Jim Ross]

What did the cam/turbo change do for you?

 

[AH64ID]

Smoother bottom end, cooler EGT's, more top end power from lack of drive pressure, dropped the cruise boost to 2-3 at 65 and 4-5 at 75, 5-10% increase in fuel economy, and generally more fun to drive!

 

[cerberusiam]

Forgot to answer the EGT question. It stays in the 800-900 range at 70 mph and the boost runs pretty high (compared to the old '01)... . usually in the 20's.

That is towing or head into a +50 mph wind, correct? The EGT's are not bad but empty boost should be about 9-10 psi, maybe 12 on good grade. A reading of 20 psi at steady cruise in normal conditions is way abnormal. That may depend on how your reading it also.

I guess I would consider doing the cam and turbo change... . IF I am convinced that I could get the mileage up to 16-17 minimum.

Don't do it expecting a big change, never seen it work yet. There is another inherent problem there that is causing the excessive fuel consumption and trying to change it with a turbo and\or cam is not going to work.



Before doing anything else I would look closely at the injectors to see if they are the root problem. You don't know the history of the truck so you don't know for sure what has been done. Quite frankly, with an 07 I would even consider a new ECU before dumping too much more $$ into add ons. There is something about the CAN systems and the ECU that causes all sorts of problems with no indications.

 

[Jim Ross]

What would I look for with the injectors?
Although I have no real reason to say this, I have to wonder if there may be an issue with the AT or torque converter. Nothing is obvious to me with these components, but could there be an issue here that might be a major contributor to the poor mileage? All the fluid changes/maintenance items are up to date.
As I said, I bought this truck used and it had a goose neck hitch on it, so I know it was used for towing in its previous life. I bought it at auction and it was a bank repo.
I'm just fed up with its rotten mileage and am about ready to sell it or trade it off and find something that will give me 17-18 running empty.

 

[cerberusiam]

A typical trick to increase power and try to help mileage was 50 HP injectors. In most cases, if the mpg was bad to start with it got worse. Just one of the things that was\is done and if you don't know th ehistory it is hard telling what is in there.



Those numbers you posted for temps and boost, was that empty or towing? 20 lbs of boost empty is indicative of either over fueling or something dragging.



Could the trans be the problem, maybe. Hard to tell unless you know how it pulls and feels and shifts compared to one that gets better mpg. However, anything serious enough to cause that much of mileage drop is usually going to render the truck dead in the water sooner rather than later with an auto.

 

[Jim Ross]

The numbers were for towing the 18 ft box trailer (trailer empty). The trailer is a flat-nose style, so it pushes a lot of air going down the road. But still..... this truck's mileage running empty with no load is worse than what my old '01 got pulling the 27 ft 5th wheel trailer.

 

[cerberusiam]

Was your 01 a dually? A 4x4 auto dually is just about the worst configuration for mileage there is.



If adding a Smarty and adjusting the timing doesn't make a significant difference there is just somethin off somewhere. To get 17-18 at 70 mph with even a SRW take some tweaking becuase if the aerodynamics and weight.



It may very well take some massive changes to get even close to what you want.

 

[Jim Ross]

My '01 was not a dually and I know that will make a difference, but the '01 was able to pull the box trailer on a level stretch of road at 65 mph and still have 700 EGT and 10 or less boost pressure; this '07 running empty, not towing, runs at 800 EGT and the boost pressure tends to be above 10 most always. I have never been able to get it to run as low as 600, no matter how I try to drive it... . and it takes a long time to cool down to get it below 400 deg.
I have noticed that this truck produces smoke almost all the time: it smokes a little at idle on start-up, it smokes a little idling down the street and it produces smoke when pulling gently away from a stop light. It doesn't pour out a huge cloud of black smoke, but it puts out enough that I can see it in my passenger side mirror. Is this smoke and EGT level "normal"? All the above is with stock settings.
Currently, I am driving the '07 without the inside duals, but so far, it does not appear that this is going to make a difference in anything (except for improved traction on snow).

 

[AH64ID]

The numbers were for towing the 18 ft box trailer (trailer empty). .

That makes a little more sense!



What are they empty?



What settings were you running on the Smarty Jr?

 

[Jim Ross]

this '07 running empty, not towing, runs at 800 EGT and the boost pressure tends to be above 10 most always. I have never been able to get it to run as low as 600, no matter how I try to drive it... . and it takes a long time to cool down to get it below 400 deg.
I have tried just about every combination with the Smarty Jr. I notice a little bit of "seat of the pants" improvement in the SW3 mode, but the smoke is terrible and there is little, if any, difference in the economy and the numbers are pretty much the same----maybe a tiny bit lower EGT, but not much.
The above numbers are running totally stock settings.
I'll be off line until tonight, heading to Idaho from Reno, the better 1/2 is "waiting on me" now. Driving our '06 GMC 1500 today and leaving the Dodge in Reno.
Looking forward to more talk, thanks.

 

[Mark31]

If you asked the bank that had the truck to ask the former owner to call you, maybe he could give you some clues about where to look. A sincere "please" and "thank you" still go a long way. You've got nothing to lose! Mark