fuel economy 05 duramax

CBRJohn2000 · Aug 6, 2005

I have a 05 CC LB, completely stock until yesterday. The only change I have made is adding a bedcover. My millage has been consistant at 16 to 17 MPG combined city and highway. Yesterday I installed a Snug Top Bedcover and did some testing by resetting the DIC millage calculator while driving on a level section of highway. My Millage before snug top was as stated above when I did this, this test however it showed 21 to 22. (at 65MPH).

I have only put 100 miles on it so far, so time will tell for sure if this is going to be my overall results. My thoughts however are that I will see some increase due to the loss of drag from the tailgate. I will keep you all posted over the next couple weeks.

I would be interesting to take a poll of millage differences LB vs SB, CC, vs other cabs and so on. I understand that a heavy foot will decrease, and I do have a hit of a heavy foot so I will never get good millage in town. I have to live with my heavy foot in town and take a loss in millage.

Something for everyone to think about tho.......

John

cjk · Aug 6, 2005

The amount mileage varies in these trucks amazes me.
I guess I'll have to be happy I got a good one.

I'm getting 20-21 consistantly as a daily driver (hand calculated). The DIC is usually within a half mpg with calculated figures.
Mileage does DROP pulling my 5er though. Got 11.5 on a 400 mile tow last week across Ohio. I was surpised how much the trailer drops it, but my last truck had a 8.1 gasser. It only got 5-6 towing. Makes 11.5 look good!!

1st diesel, 5500 mile on the truck, so far I'm impressed to say the least.

turbov6joe · Aug 7, 2005

My mileage sucked until I hooked up my 25' enclosed car hauler with car, tools, gear, etc.... read HEAVY! I then pulled from Paola, KS. to Bowling Green, KY. hauling ass at some points. In other words, I was running like I ganked the truck/trailer! When I came back mileage was up significantly. Pre-Trip = 12-13 mpg Post-Trip = 15-16 mpg. My rig is a 3500 DRW, CC, Duramax/Alison, 4x4 with approximately 5500 miles on the clock. Currently the only mods are a Predator on 65hp and no muffler....I have a 4" cat-less downpipe on the way. On a flat unloaded run @ 70mph I can see 19-20 mpg no problem on summer fuel.

ronadijcks · Aug 7, 2005

Forget the MPG's. I JUST PAID $2.999 FOR DIESEL FUEL.

Can someone help me UNDERSTAND how it is possible for the guy next to me filling up his Mercedes with Premium, is paying 25 cents LESSSSSSS than me gallon?
Is it just CALIFORNIA, the land of being screwed? OR everywhere?

What is happening? The argument for a diesel is dwindling....

Melvin Hatcher · Aug 7, 2005

BigShrimpah said:
I am not dilusional about my mileage, and I don't even use my DIC because the predator throws it off big time. I DO GET 21mpg @ 72ish mph cruise and a/c on and this is hand calculated and fuel filled to the same spot every time. Maybe the EGR block off, my catless front pipe, and the predator helped me, because when it was new I was getting about 18mpg hwy.

My set up is close to yours, I have the predator, my EGR is not blocked off, I still have the cat intack however, I do have the MBRP cool duals on my truck.
Before installing the predator, running with the four inch dual pipes my truck empty was getting on the road milage 19-20 mpg @ 70 mph, hand calulated. With predator it will get 20-21.7 mpg, under the same conditions.

MEANMAX · Aug 7, 2005

EZ set on 30 on "hilly" trip doing 70-75 mph,18mpg. Around town 17-19mpg(all hand calculated).

bthompson · Aug 15, 2005

I have a 2004.5 LLY 2500HD. My truck's DIC life average is 12.4. I do not have a lead foot. When pulling my trailer, which is not often I get low 11's. On the highway it gets high 14's or low 15's. I have Edge w/ Attitude, TrueFlow intake, Roll n' Lock cover, and slightly bigger tires. I was told that the LLY would get better mileage than the LB7, but I have three friends with 2003 or newer LB7's and they average 16.4. I have seen their DIC's.
The only thing I do not have is exhaust. Since nothing has made a difference I find it hard to dump another $600 or $700 into the truck. I have read numerous posts and have too seen astronmical numbers for MPG (compared to mine). Should I take it to the dealer? Can anyone give any suggestions? I keep looking for some magical reason that I get 4 to 5 MPG's less than average. With gas prices so high, that 100 miles a tank is a huge difference. Help!!!

chp777 · Aug 15, 2005

how many miles bthompson just wait out of the blue your miles will just change thats what mine did. i started to doubt what everyone said they were gettng for mpg then mine changed from 15.5 to 17.5 now i'm getting 18.5 t0 20.2 this all happen in 3 weeks time and i only have 2200 miles on it. when i hit 19.7 i took a pic of it i was so happy lol. it's the little things in life that makes us happy i guess :rockit:

S_Tigue · Aug 15, 2005

Let me start off saying I am brand new to this forum. I traded my 01 8.1 gas dually for a brand spanking ne 05 crew cab dually. I am cosistantly getting 15.2 with the cruise set at 70. In town low 14's to high 13's. looking to increase milage I had a "areo turbine 4040L" muffler installed and as well had the cat cut out and strait pipe installed.Now here's where it gets interesting. Upon leaving the muffler shop heading back to my shop the milage jumped to 19.4 with the cruise set on 70 and that treck covered about 15 miles of highway . I got to my shop and the truck sat for about 2 hours and then I left to make sales calls which was all over the D/FW area. I noticed with the cruise on my milage went to about 15.5 at 70 with the cruise on . I can't figure that one out how it would jump so high then come right back down. There is also something else , now i have this smell around the truck and inside. It's almost like a exaust leak getting in the AC .I checked the strait pipe where the cat was but the welds are really good and not leaking. Oh i have about 7500miles on the truck and about 300 with the new exaust. Any help or opinions would be much appreciated. Thanks

chp777 · Aug 15, 2005

well you will smell more diesel smell with the new exhaust i just put my exhaust on today and i can smell it now also the old big muffler was like a filter and so was the cat.as for the mileage i was getting the same before the exhaust and really no change with the exhaust. on your next fill up reset your dic and see what you get first

cbm · Aug 15, 2005

I just got mine and it had 5900 miles on it (dealer demo).........I have put about 600 miles on it so far . When I got it the DIC said 15.5 mpg ..........getting on it a lot it dropped to 15 mpg...........took a trip this weekend and took it easy.......average is back up to 15.4 mpg !! Majority of this is city driving ! It's bettter than my 5.3 liter Z-71 so I am happy........but I am not sure if it'll get better than 15-16 mpg around town !

S_Tigue · Aug 15, 2005

the diesel smell is al around the cab. When I stop at red lights it can get bad enough to bother my eyes inside the cab with the ac on and windows up.

bthompson · Aug 15, 2005

Sorry....I forgot to mention that I had 18,000 miles on my 2004.5 LLY. I appreciate your outlook chp777, but mine has never, ever, gotten 15.5mpg. I consistently get 12 or 12.1 around town. When I say that I am a slow driver, I mean it. I have all of the add-ons and do not hot rod around. I am really disappointed in my gas mileage. It is even more discouraging when I see all of the 16-20's mpgs that have been posted and I have seen with my own eyes. I do not know what else I can do. Could there be something in the manufacturing that could change my mileage that much.

Just Tool'n · Aug 15, 2005

My 05 now has 11,000 miles on it, I had the reflash done to fix the surging problem.

I drive with a really light foot!

Milage around town driving is 13-14mpg.
Freeway is 16-17mpg.

Last weekend going to San Diego got 18.1 going down, all freeway driving.

Coming back, got 16.2 MPG

The real diffrence seems to be if you drive much city driving it really seems to kill over all milage.

Bone stock, except put a snug top camper shell, whick I thoght would help with the milage.

I think the re-flash made it get worse milage than before.

colnago · Aug 15, 2005

Just Tool'n said:
Bone stock, except put a snug top camper shell, whick I thoght would help with the milage.

Everything I have seen shows that a camper shell will reduce mileage. I was also told that removing/dropping your tailgate will reduce mileage as well. I haven't seen anything about the effects a tonneau cover will have, if any.

Joseph

jjcgolf72 · Aug 15, 2005

My cap boasted mileage by almost 2 mpg. I noticed the difference right away.
City driving gets my 14.5-16, all hwy gets 18-19 at 65mph, mixed gets 16-16.5. Thats driving at startup very slow not exceeding 2000 rpms and coasting as much as possible into the red lights hoping for green. Hwy towing trailer last trip got 12.5 pulling 4000 lbs at 72 mph. I did just order a removable air deflector for the roof when trailering. I hope it works.

colnago · Aug 15, 2005

Jeff,

I noticed that you pulled a load very similar to what I had this last weekend, with similar MPG numbers, but you drove faster than I did (I kept it down to ~62 MPH, and got ~12.3 MPG with a 4000# TT). I also noticed that your signature mentions the Aero-Turbine 4040L. Did you notice much of a change in performance/mileage with this mod? Are you using the stock pipes, and adapting up to the 4" required, or did you add in a different set of pipes?

Thanks,

Joseph

bullydog · Aug 15, 2005

mnoutlaw said:
I actually checked my speedo with gps on a trip. I was within a mile per hour. The thing that makes me wonder is why my 03 got 3 mpg better with the same setup. Might put stock tires on a see what happens.

You weren't within one mile per hour, because the truck might say its going 60 but is going 59 absolute speed (what the gps would read). So, if you were 1 mile per hour off w/265's by checking your actual speed compared to the "shown stock speed", which is actually 1 mile per hour off, you are 2 miles per hour off in total compared to stock.

In theory the 265 tire on the same rim and a 75% ratio will make the truck roll 3.88% faster at the same revolutions.

So, in theory if you're going 60mph (off gps) with the stock tires, and then go the same speed (when the needle on your speedometer is at the same...about 61) with the 265's, it should read about 62.3mph. Now, that's theory!

Of course in reality, factors such as tread depth and the likes will make the numbers a bit different.

Add about 5% to what your DIC reads.

Fact though is that the lb7's just get better mileage.

Hope this helps.

Later.

SmokeyMax · Aug 15, 2005

I can't get less than 18 MPG Combined city & highway! For the pas 2,000 or so miles I haven't reset my DIC and it's stuck on 18.0 MPG. How in the world can you get less than 14 mpg not towing? If I was getting 12 MPG my truck might have to burn

I could see the clutch fan fully engaged if the engine was hot killing MPGs though.

bthompson · Aug 16, 2005

There may be something to the clutch fan. I was having A/C problems and they replaced the clutch fan & a week later it was burned out again. Could that effect my mpg's that much? If so, that might explain my 12 mpg.

Thanks for any input.

fuel economy 05 duramax

CBRJohn2000

cjk

turbov6joe

ronadijcks

Melvin Hatcher

MEANMAX

bthompson

chp777

S_Tigue

chp777

cbm

S_Tigue

bthompson

Just Tool'n

colnago

jjcgolf72

colnago

bullydog

SmokeyMax

bthompson

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