6.7L Dodge Trucks and The Fuel Mileage

[Jeb_H]

Guys,



I have been patiently waiting for 15K on my new 6. 7 in hopes of better fuel mileage numbers once broke in. I read lots of stuff of you guys getting 17-19mpg on the highway and 14 or so in town.



I get nothing like these numbers never seen anything close. I am lucky to see 13-14 on the highway and have the cruise set at 70. Pulling the 27' trailer of mine I see pretty much 10-11 on the road.



I am just trying to understand the difference in the trucks if any, mine has the 68RFE transmission and the 3. 73. Tire size on my dually is LT235/80-17" General brand tires are what is on her also.



Heck I have even tried running in 5th gear for the final overdrive instead of 6th gear. The one time I saw anything close to mileage some of you are getting was when I had a tail wind of 40-50 MPH and I was not towing anything, I ran a nice 250 miles at 70 and got 16 MPG. Was nice to see but not a real honest test to expect with that kind of tail wind...



So what the heck is the deal with this difference of mileage on these trucks??? I sure would have thought mine with the 3. 73 gear ration would have been the ticket for the better fuel mileage, so is maybe the 4. 10 the better choice? Maybe its a certain color of truck that gets the fuel mileage numbers I need to see LOL??? I fear my only hope at this point to get the fuel mileage up will be the Bully Dog enhancement once they get these out and in the forsale shelfs.



So what are you guys running tire size, transmission, dually or not and maybe even the color of these 6. 7's and the speeds the mileage you guys are getting???

 

[TConnolly]

Jeb_H,



I don't know where they get those great numbers? Here is my experience, With the stock tires on flat Florida I get 14 mpg average, with 75% draging 12K / 25% empty suburban & country roads. My best was the first 500-600 miles to home from the dealership mostly all I-75 southbound, averaged 17 mpg.



When I went to the bigger tires I lost 2 mpg, at 7k I've earned 1 mpg back.



I can say this my mileage is better than I got with my 05, It started at 10 mpg and was up to 20. 03 empty (combined / towing average 16 mpg) at 23 months / 80k. They take way longer to loosen up than anyone admits!



Both trucks never more than 4 hours from home, so no long trips.



Tom

 

[y-knot]

Look you guys are not going to get any appreciable mileage change from new to 45K, and whats more the new trucks are not going to get any more mileage then the older trucks, 8-9000 lbs just isn't a good recipe for high mileage.

 

[CUMMINZ]

With 250 miles on my new 6. 7L dually with 4. 10s, I ran my first tank full out from middle NC to Wrens, Ga. yesterday. Stayed at speed limit and got hand calc of 14. 25mpg.



:-laf

 

[Jeepstang]

Jeb I have the same setup as you and almost 500 miles on the truck the best I have seen so far is 14. 1 i would like to see the 16-19 range I read about as well

 

[TKeeler]

With 250 miles on my new 6. 7L dually with 4. 10s, I ran my first tank full out from middle NC to Wrens, Ga. yesterday. Stayed at speed limit and got hand calc of 14. 25mpg.



:-laf

As I posted in another thread my last fill up numbers were 280. 5 miles and 16. 5 gallons or right at 17. 0, the info center showed as high as 18. 1 during that trip. There wasn't a lot of stop and go driving but I did go through some small towns along the way and some mountain pass's. For those of you familiar with the area it was from Mt. Vernon, OR to Junction City, OR. I really believe that there may be some 'sweet spots' for these trucks and where they get the best mileage. . in the short time I have been driving it it seems to get the best mileage (according to the info center) at 60 mph and 1700 rpm.

 

[CUMMINZ]

I'm not concerned at all with my milage with only 500 miles on my truck. That is better than what I got with my new 04. 5. It took 5000 miles for it to get better.

 

[jelag]

I need to add a couple of things here... . I own 3 3500's with the 5. 9L and empty we see 17 or so on the highway taking it easy and 11 to 13 heavy towing...

2 of the trucks have the 410's and the other one has the 373's... the one truck with the 373's driven at 10 mph under the limit at say 60 will see close to 20mpg.

Mileage is a factor based on weight, wind resistance, rolling resistance and the speed in which you accelerate..... I've spent maybe close to 1000 hours on a dyno years ago with gas engines... . these big dually just won't do much better.....

Hope this helps... BTW I personally think you won't see good mileage till you get to at least 5K miles... so at 15K you should be there... . and I'm guessing its not going to get more than 5% better.

 

[Jeb_H]

This all looks about like what I have been thinking, but there are those here local that keep telling me that I should see better.



Heck my old 95' Ford PSD F350 gets this kind of mileage and that is a 13 year old truck too LOL. Must admit I had hoped for a little better and still hope that the Bully Dog PMT I hope to put on soon will help some...



I was just somewhat worried if there are thopse with basically the same setup as my 3500 was getting much better, that maybe there was something wrong with mine is all. She does pull good, quite impressive when you stop and consider what our fearless Gov't has stuck on the exhaust of this poor diesel motor



Thanks guys

 

[JTCHess]

Interesting mileage numbers. I was looking at a 2 year old used Mercedes Sprint RV conversion van yesterday and the owner claimed to average 22. 9 MPG. I would think that these trucks unloaded should get this. I become less and less convinced about the economics of diesel power when a diesel starts getting the same mileage as a big block gasser, with diesel fuel costing 20 to 30 cents more per gallon, and the significant upfront option costs are considered. I know they'll last a million miles but, other then commercial users, how many folks actually keep a truck that long. Not us RV types. Heck my 93 D350 only has 75,000 miles on it.



John

 

[jcarey]

Good points, but I think, cubic inch for cubic inch, you still get better pulling power with a diesel. That can be important on those long hills.

 

[Wolfy]

Mileage Expectations

I need to add a couple of things here... . I own 3 3500's with the 5. 9L and empty we see 17 or so on the highway taking it easy and 11 to 13 heavy towing...



2 of the trucks have the 410's and the other one has the 373's... the one truck with the 373's driven at 10 mph under the limit at say 60 will see close to 20mpg.



Mileage is a factor based on weight, wind resistance, rolling resistance and the speed in which you accelerate..... I've spent maybe close to 1000 hours on a dyno years ago with gas engines... . these big dually just won't do much better.....



Hope this helps... BTW I personally think you won't see good mileage till you get to at least 5K miles... so at 15K you should be there... . and I'm guessing its not going to get more than 5% better.

Going a bit afield here, but some thoughts on realistic expectations:



In 1995 I experienced the best mileage I have ever personally gotten from an automobile. On a trip from Salem, Oregon to Reno, Nevada, driving a six mo. old '95 Honda Civic (VX, I believe was the model - the little hatchback), two people and light luggage aboard, at 70-80mph, all "highway" driving, some mountainous, we averaged 56 mpg.



I expect people to doubt this figure,... I was shocked(!), and so very carefully checked my math during several fill-ups. My wife is still driving that (now high--mileage)car today,. . nearly all city driving, and averages around 40 mpg.



The fact that I am talking about a 12 year old car, and today's manufacturers are bragging about approaching 40 with their newest fuel-efficient models, is one of those things that makes you go "Huh?".



What have they (including Honda) been doing in the years between? Incidentally it is reported that this model is a high theft-target among young would-be mini-hot-rodders, and we have been asked in traffic by some youths in a car alongside at a stoplight, whether we wanted to sell the car. It does perform very well for it's horsepower! (But, with the wheels off, looking at those little toy brake-drums will SCARE you! )



Now to the diesel pick-up reference: When one considers that these trucks as-discussed and used, are easily 4X(or more) as heavy as that fairly-sleek little Civic, and have, with their camper/trailer/5-ver, etc. , maybe 4X the air-resistance as well, ... and when the geometric increase of this factor and power requirements with speed is considered(squares, cubes), ... is 12-14 mpg when towing or hauling fast really surprising? 56/4=14 (for example).



Maybe these CTD's are doing quite well after all,... considering just what it is they are doing



Seems to me the biggest factor in the mileage-disappointment thing is the speed at which many set their cruise controls (70-73?).



I'm betting old-man speed (60-or-so) would change things considerably for the better.

 

[hammersley]

But let's be realistic here - we've killed the mileage thing ourselves - don't entirely blame EPA- we want more HP... THAT COSTS! Look at the Big Rigs - Pulling 80,000 lbs AND getting 8. 5-8. 8 MPG! That makes us pulling 20,000+ and getting 10-11 look like a GAS HOG! But then again they don't accelerate and maintain speeds like we want now. If we didn't let the macho thing get in our way - me included - we'd be spending a lot less on fuel! We should look carefully at going backwards in HP - I mean lower it to get better mileage... Oh I hear the vendors now ---- but you simply can't go faster with more power and get better mileage - ain't gonn'a happen! Maybe the old days of 160 HP whould be re-thought... ... ... ... ...

 

[TKeeler]

Interesting mileage numbers. I was looking at a 2 year old used Mercedes Sprint RV conversion van yesterday and the owner claimed to average 22. 9 MPG. I would think that these trucks unloaded should get this. I become less and less convinced about the economics of diesel power when a diesel starts getting the same mileage as a big block gasser, with diesel fuel costing 20 to 30 cents more per gallon, and the significant upfront option costs are considered. I know they'll last a million miles but, other then commercial users, how many folks actually keep a truck that long. Not us RV types. Heck my 93 D350 only has 75,000 miles on it.



John

I got 141,000+ miles on my 98. 5 and it still runs very, very well... you wont get that out of a gas motor. Finally diesel fuel is less than gas

 

[courierdog]

Here is my 2 cents worth, Same 2000 mile trip carring the same passenger weight, 2 people plus one Rottweiler, 2005 Jetta TDI wagon 48 MPG, 2007 Dodge 6. 7 20 MPG. The quiet ride in the Dodge is worth the extra fuel. Plus now I get to carry more in the trade, light courier work. Here at home in Alberta, diesel runs at 83 cents per litre as opposed to gas at $1. 09 per litre.

 

[2Rowdy]

Heres my number I have 7500 miles on my truck and the average over those miles is 13. 7 mpg. Some towing but mostly no trips shorter than 25 miles on highway. Not much town driving.

 

[BBeck]

I average 15.5mpg

I have been averaging 15. 5mpg since new. However, my last fill up was 14. 1. It was mostly town driving. Take a short round trip on the highway and it jumps up quite a bit. I live in a very hilly area and my tires are 60psi front and rear.



I went to the dump the other day and the truck is weighed when you leave. I was shocked to see that with my setup and only me in the truck, it weighed 8040lbs (full tank of fuel). So much for 7400. That means that my payload is really less than a 1k and not really the 3/4 ton.



Brad

 

[Sasquatch]

I have right at 10,000 miles on my 6. 7, and it's settled down to a predictable 15-16 mpg on rural roads that feature small towns, lots of intersections (housing developments), shopping centers, stoplights, and 55 mph speed limits.

It I get out on the interstate, and keep the speedometer set at about 60-62 (a tad over 1500 rpms on the tach) I get a consistent 17-18 mpg, depending on terrain and wind.

Towing my 16' enclosed trailer almost always yields 10 mpg, but can drop down to 9, if I push the truck along at 70 mph, or if there's a wind.

I really don't see much of a difference between this truck (fuel penalty wise) and my old 12 valve '97, 2500.

I did get 2-3 mpg better with the old truck, but that was in the days of better fuel, and that was in a truck with two less tires and substantially less wind drag.

Jusat about everyone -- including the 2nd Gen truck owners -- will readily admit that they've lost a couple of mpg with this crappy new fuel we're being asked to burn, and it seems to me -- when you factor low-btu-fuel into the equation -- that we should be pretty pleased with the mileage we're getting from these new trucks.

 

[JWhitman]

I just got back from a 500 mile trip averaging 55 mph over very hilly terrain up in the mountains and got 19 mpg. Prior to that I have been averaging 14 in town and some light rural driving. I have towed sparingly and was getting about 12-13 with a 5k camper trailer.



Jason