Not to start a new mileage thread, but I figured out the formula for 21mpg (21.8 on the DIC)...


Drive 55.


I was on a stretch of road for about 300 miles round trip along the north shore of Lake Superior over the weekend. I took it easy and never went above 60. The road winds a lot and is a little hilly (by Minnesota standards), but I guess it evens out when going both ways. The good news is that after only 2000 miles on the truck I can already see the improvements in mileage. Heck, at this rate, I will be at 50mpg by the end of summerhttp://www.dieselplace.com/forum/smileys/Big Smile.gif


On a side note, my DIC has consistantly been reading about .5 to 1 mpg better than actual.Edited by: sammy

I figured out the formula for 21mpg (21.8 on the DIC)...


Drive 55.


Wouldn't that take all the fun out of driving?http://dieselplace.com/forum/smileys/Big%20Smile.gif


I'm just bein' a smart ass.


I'll be happy with a consistent 15 mpg.





Gar

Hell I drive 70+ all the time and the worst I have seen has been 16.5 and the best was on cruise about 200+ miles non stop and I was getting close to 18 mpg. At least that is what the DIC said. Managed to get over 450 out of that tank. So not bad.

As the song says "I can't drive fifty five"!

Yep, 55 will get ya 20+. Just can't drive that slow anymore, only seems like few years ago and the whole nation was 55 stay alive, now anything under 80 gets you run over. On a side note, just did a 700 mile round trip at an average of 67mph and got 16.5mpg with a 600lb 4 wheeler in the bed--2000 miles on the truck so far!

I agree with the DIC info. Mine is off about the same. I can get those number driving unloaded at 65mph. In the flat rice lands of katy, Texas

Sammy
I see you have 265's, how did you compensate for the added diameter of the tire?

Race,


I had the dealer reprogram the computer with the Tech II so everything (speed & distance) is right on when checked against my GPS.

Interesting... I will have to try this.

Going to be tough rolling down I-90 at 55 though - I get dirty looks when I set the cruise at 65...

The road that I referenced is a single lane with 55mph, so staying within the limit was not too much of a stretchhttp://www.dieselplace.com/forum/smileys/Approve.gif


I anticipate that I80 across Nebraska at 80mph into a 30mph west wind will be a different story (that is why it is called "I80", right?).

I drove 200 miles the other day and about half was driving 65 and the other half was 70 on the Interstate. And both were a little hilly. I had the 120 hp Attitude in and the computer said 23mpg and I check it and was really 21.

Race,


I had the dealer reprogram the computer with the Tech II so everything (speed & distance) is right on when checked against my GPS.





Really? This is interesting. Last I heard, the Tech II will only reprogram the ABS for differences in tire size. It won't do anything for speedo/odo correction.


Dmaxallitech, is this something new in the '04s?

on a 100 mile freeway that I just filled up before I got 20.6 with the speed ave at 61.

My DIC consistantly reads .5 to 1.0 MPG too low, but it hasn't been reprogrammed for my 265 tires. I use my GPS to tell me how many miles I've actually driven. If I'm on a two lane road with a 55 MPH limit, I always get 20+ MPG according to the DIC, but as soon as I hit an interstate & 70+ MPH, my MPG drops to around 17-18 MPG, (depending on wind direction & speed) according to the DIC.
BTW, my truck is just over 2 months old with 14,006 miles & 336 hours. Love the truck.http://www.dieselplace.com/forum/smileys/Thumbs Up.gif

You think the 265's change the MPG that much? I added them with about 900 miles on my truck and was getting about 16.5 now with them I am at the 15.5 range. I was thinking that I just was doing more true stop and go and that was the diff. I did not think the tire size would impact that much. I see the 1 or 2 mph at 60 diff but the .5 to 1 mpg diff surprises me.

I changed over to 265s with about the same mileage as you, & it was too early to tell how it affected my fuel mileage. I would THINK that it helps slightly. I was just trying to point out that if you change to a larger tire size, the DIC will show lower MPG, but your actual MPG won't neccessarily be lower.
My odometer is off 4% now with the 265s. Take 18 MPG, for example. 4% of that is 0.72, which would lower your indicated MPG on the DIC from 18 to 17.28, since it thinks you're traveling fewer miles on the same amount of fuel.
Hope I'm making some sense here.http://www.dieselplace.com/forum/smileys/Confused.gif

The dealer should have no problem reprogramming for 265's. I think the reprogramming problem comes into play when going to larger tires like a 285+. Besides, the new 3500's are available with 265's from the factory.

The tech II, based on my memory, does not recalibrate the speedo, but only the ABS. I had mine adjusted to 265's and the speedo is still off. The new SRW 3500's have the tire size programmed into the computer allready since that is the only tire size they come with.

After programming with the Tech II, my speedo is "dead on" when compared against my GPS.

The tech II, based on my memory, does not recalibrate the speedo, but only the ABS. I had mine adjusted to 265's and the speedo is still off. The new SRW 3500's have the tire size programmed into the computer allready since that is the only tire size they come with.


I don't think there is anything to reprogram as far as ABS. Those sensors don't care about actual speed, just when the fronts are going noticeably slower or faster than the rears under braking.

I am torn about having my speedo changed with my 265's. Someone did the math and you get an extra 4200 miles on your warranty and 12800 or something like that on the engine warranty. I just remember I am +1or so at 60 and am getting a little better MPG.

I made a trip this weekend of about 900 miles round trip.


With my Edge Juice on Level 3, I got 21.8 on the first 450 miles.


On the return 450 miles I got 21.6


My total trip avg MPH according to my gps was 74. I ran up to 90 for a long stretch.


The last time I made this same trip at almost identical speeds, I got 18.6. So in my case, my juice gave me better MPG :)

I notice most of you have 4X4's, I have a 2WD D\A CC on order and am wondering how much better 2WD milage will be than a 4X4??

I notice most of you have 4X4's, I have a 2WD D\A CC on order and am wondering how much better 2WD milage will be than a 4X4??


I just put my first refill in my 3500 DRW CC LB 4x2 and got 16.6mpg (17.3 DIC). The DIC started out at about 14 and steadily climbed for the first tank as it was broken in. I know have 1000km on the truck and the DIC right now is showing 18.5mpg for mixed driving. I suspect it's probably high 17s. So far I'm extremely impressed given that the engine has only been running for 4 days. :)

Andrewfessler,


Make sure you calculate your mpg by hand, because the juice throws off the DIC, and makes it look like your getting more miles than you really are.

Well, gotta throw in my 2 pennies here also. I have had my '04 dmax/ally for about two months and have put 5400 miles on it. I drive 100 miles per day highway at 70-80 mph. I average 16.5 mpg at every fill up that is DIC, actual calculated is 15.5! On the only two trips I have done were 660 miles round trip both hauling a 600lb load in the bed. and one was 16.8 on the DIC and the other was 15.9 on the DIC (that one I had the AC on) Finally, my calculated mpg are always 1 mpg lower than the computor! My truck is bone stock. So, either you guys are BSing, or my truck just plain sucks, cause I ain't never seen 20mpg doing 70 mph!!http://www.dieselplace.com/forum/smileys/Angry.gif

sounds like an angry 2 pennies. I have my first road trip coming up but I average 15.5 ac off and around 25MPH ave. My down fall is I live on a hill that is 10 - 12% grade so going up hill sucks down my ave and I do it several times a day. If I stay off my hill and do a lot of around town I see 16 to 17 mpg with 26mph ave.

Not angry, just figured it would out perform my old truck, it got 18mpg on the same trip ('98 5.7 gasser), guess when you put 160k on a truck you always compare it the next truck to it. Acceleration is about the same too. And towing/braking the new truck wins hands down!

yeah I know what you mean, I just have to keep telling myself I have a lot more truck, in weight, power and pulling and still get "good" gas mileage. My freeway trip will be interesting. I will be doing 200 miles freeway, hook up my new 5th wheel and towing it back so I will get some new info as to what it will do.


Cheers


TC

Redneck,


A better comparrison would be to drop your 98 small block in the new HD with the Allison & 11.5" gear. With the added weight & required HP to turn the larger running gear, I think you would appreciate the mileage & power of the Dmax.


As I stated at the start of this post, my best mileage was 21 on a 300 mile trip at 55mph. I would have been lucky to squeeze 15 out of my 6 liter in the same truck (minus allison & large rear end). I think the mistake many people make is that they think moving from a 1/2 ton with a 4.8/5.3 to a truck that is significantly heavier & much more power will magicaly provide huge mileage gains.


I am sure the big 3 could provide us with trucks that get better mileage than what we are seeing, but then we (including me) would be screaming about the lack of power! However, I am enjoying the fact that the local gas station is selling 87 octane for 1.99, while diesel is 1.70.http://www.dieselplace.com/forum/smileys/Big Smile.gif

I find these mileage threads interesting especially with the low mileage trucks. Getting a tank or two or three of 21+ doesn't mean anything. It takes several thousand miles and at least a full year to get an average. I have approximately 38K non-towing miles on my truck. This was approximately 50% around town and 50% on the highway at 73-75 MPH. My average is 18.58 . It is beginning to look like the 265s have cost me a little mileage but it is a little too soon to say. I have towed my 10K 5th wheel approximately 7500 miles. The average is 12.21. The vast majority of these miles was between 65 and 70. Later! Frank http://www.dieselplace.com/forum/smileys/Big Smile.gif

I had been towning a 28 ft fifthwheel trailer with a Chev 2500 6L gasser and AT.


I got right at 10 MPG towing. I always tow 58-60 MPH, mainly in deference to trailer tires which tend to get hot.


In town to/from work solo I got about 13 MPG.


On the highway solo I got 15-16.5 MPG (driving about 65 MPH).


I'm looking for better numbers with my new Duramax:


Hopefully about 12, 15 and 19 MPG respectfully. But that's not why I got this truck; I got it for the power pulling my trailer.......I retire 1 July this year!http://www.dieselplace.com/forum/smileys/Clap.gif

...I have towed my 10K 5th wheel approximately 7500 miles. The average is 12.21. The vast majority of these miles was between 65 and 70. Later! Frank http://www.dieselplace.com/forum/smileys/Big Smile.gif


Hello Frank. Yeah, I think you are correct. I've been pulling a 28 ft FW probably close to yours in weight for about 4 years with my prior truck (Chev 3500 6L gasser). The mileage improved a little as the odo rolled through 10k. Let's face it - I drive like an old man, but it's better for the components I think and I save a bit on fuel!


I have a buddy with an 02 DMAX/Ally and he's getting 11.5 - 13.0 towning, so your numbers sounds reasonable. I didn't get the diesel for the mileage in any event, but for the POWER!!http://www.dieselplace.com/forum/smileys/Clap.gif


Do you have much experience towing in the mountains? I do not, we are restricted to the SE USA until I retire later this year. I only used my gasser on one steep hill south of Ashville NC a year ago. I got up okay, but I was revving pretty high in 2nd at the time. I know the DMAX will do a lot better, but how is the DMax/Allison combo on the downgrades? I had no problem with the gasser with it's big engine slowing me down, but how is the diesel at that task? I am more concerned with going DOWN than with going up. PS - we have a trip out west planned for next spring and I'm studying the "Mountain Grades" book...I forget the exact title. Terrific book though.


Thanks.

Ok well set a new personal record over the weekend. I drove from Houston to Corpus then to a small town about 60 miles from Corpus then back home to Houston. Round trip was about 500 miles and I drove between 72 and 75 mph the entire trip with the cruise on. Worst I saw was 18.8mpg and the best was 20.2 on the entire trip. Truck has about 7800 miles on it now so I think that is pretty good if you ask me...


I am proud of my Dmax and I think I will keep it ..http://www.dieselplace.com/forum/smileys/Approve.gif

Was that calculated by hand or by DIC ? How many hills involved or mostly flat? I can only get around 17-18 at 68mph with cruise and some decent hills and that is by hand. I have i think 4100 miles on her now .Edited by: FASTOYS

I calculated using both methods. They were both pretty close. DIC was a little lower, that is where the 18ish came in. The other was done by paper and pencil. The drive was mosly flat some hills, usual highway driving and overpasses. Nothing major and I did not stop very much, I think twice going both ways. I think if I would have slowed down some then it would have been better. I will see what I can do on the next trip, going to Vegas soon and I will test it, going to try to drive 70 the entire trip, so that will tell. I will post results.

With 39298 as of last night, I have a lifetime average of just under 16. My normal highway is around 18.3 and in town is 14.8 now with the 265s. I was seeing 15.5 in town with the 245s. I had one trip at over 22, but to this day, don't know what was differenthttp://www.dieselplace.com/forum/smileys/Confused.gif. I would think 4x4 hurts me some as well. I know the Allison is worse than the hand shaker too. I run in Level 3 all the time and do try to keep my foot out of ithttp://www.dieselplace.com/forum/smileys/Embarrased.gif. Sometimes you are just forced to stand on it when some yo-yo is in your way or acting like an id10t trying to make you http://www.dieselplace.com/forum/smileys/Angry.gif. I do laugh when a gasser tries to pull away from me http://www.dieselplace.com/forum/smileys/HiHi.gif and I don't even have to try to leave them. If I'm in a particularly foul mood, I will do it in a cloud of smoke and a hearty Hi Ho Clydehttp://www.dieselplace.com/forum/smileys/Big Smile.gif.

It is the 70-80 mph that it getting you the 15.5-16.5 mpg. The mileage is best at around 60-65mph and will drop considerably at 75 and up. I have averaged on a 400 mile trip on I-95 taking it easy on the pedal in cruise most of the way 22.5 MPG average, doing 65-67 where the speed limit is 65 and 70-72 where the speed limit is 70. Running around town in traffic, it always averages out to about 17.3 per tank. You will get around 15-16 mpg average driving 75-85 on highway trips. If you watch your Instantaneous mpg gage, you will see real fast what constantly punching the pedal does to your milage and you will end up getting 12.5 -14 mpg on the average around town. In these Dmaxes the average mpg is really dependant on how you want to drive. I have had 2, both LB7's, and I put a lot of miles on them, mostly long trips. I have got the mileage thing down.

My mileage seems to be improving slightly... not sure if it's the fact that the truck is starting to break in (~6,000 miles), the Magnaflow cat-back, or both.. but my last 1.5 tanks have seen almost a 1mpg improvement. I went from averaging 17.2mpg to 17.9, and I have been driving faster to boot (17.2 was not exceeding 65mph on the expressway... but the last 2 weeks I have been doing ~70.) Truck seems a little quicker too.

I really wanna try for that 20mpg mark, but I just can't bring myself to drive 55.