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Old 11-10-2008, 11:27 AM   #1 (permalink)
andym1996
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LMM Good Mileage! (a change of Pace!)

I keep seeing these negative posts about LMM Mileage, and it really is getting frustrating . We all understand the Regen Process Kills the Mileage of these rigs.

This Past weekend i took Duramax up north pulling my old '79 Dump Truck. I experienced really great mileage even through a Regen Process while pulling the approx 12,000 LB Load for approx. 300 miles. (Hand Calc'ed - 11.9 MPG - Ran at 65 - 69 MPH).

I left the '79 up there, and headed out with just the truck. Temp was 19-25 degrees, no cold front. I ran at 68-74 MPH for the 300 mile trip, and saw 20.8 for the run home. Tires showed 74 in front, 79 in rear. All Factory as you can see.

I did notice that running the 5w-40 Synthetic CJ-4 Oil made a difference of 1-1.5 MPG. It costs a touch more, but i think well worth it for the cold starts, and mileage that i have witnessed.

Just a little positive for the day.

Andy
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Old 11-10-2008, 11:40 AM   #2 (permalink)
JIMMMY
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Just switched to Syn at 15K miles too - and saw no increase in MPG over a 700+ mile trip. Just put on winter tread, maybe that will make a dif.
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Old 11-10-2008, 02:25 PM   #3 (permalink)
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I've just turned 29000 miles and was experiencing horrible mileage (9-11 mpg loaded, 13-16 mpg unloaded? In the last 5000 miles I'm getting 13-15 mpg loaded and 18-21 mpg unloaded. Same loads, same foot but it did creep up some. I was using the Econ 1 setting on the Evo, before and after the reflash and for quite some time I was getting discouraged. But somewhere around 25,000 miles it settled in.

I've been very curious as to running a Hydrogen setup in the truck. Maybe after 36,000 I might pull the trigger. I have a pretty savvy Hydrogen system here locally for about $2200.

James
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Old 11-10-2008, 02:48 PM   #4 (permalink)
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I run a Banks 6 Gun and Monster Exhaust on my '08 LMM, and there is NO discoloration in my exhaust tip. I installed the Banks package in April, and monitor the DPF regens on the optional Palm PDA. I haven't seen more than one or two regens since I installed the Banks package; before that, I have no idea when or if it regened. I have 25K on the truck now. Absolutely stock, one month after I drove it off the showroom floor, I averaged 16.8 mgp from Dana Point, CA to Portland, OR and back. A month later, with a hard bed cover, the same run I averaged 17.2 mpg. With the Banks package, the same run would probably be at least 20, maybe 21 mpg. I run Amsoil SAE 5W-40 Premium API CJ-4 Diesel Oil.
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Old 11-10-2008, 06:40 PM   #5 (permalink)
andym1996
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Quote:
Originally Posted by jlsworks View Post
I've just turned 29000 miles and was experiencing horrible mileage (9-11 mpg loaded, 13-16 mpg unloaded? In the last 5000 miles I'm getting 13-15 mpg loaded and 18-21 mpg unloaded. Same loads, same foot but it did creep up some. I was using the Econ 1 setting on the Evo, before and after the reflash and for quite some time I was getting discouraged. But somewhere around 25,000 miles it settled in.

I've been very curious as to running a Hydrogen setup in the truck. Maybe after 36,000 I might pull the trigger. I have a pretty savvy Hydrogen system here locally for about $2200.

James
Quote:
Originally Posted by shadowm View Post
I run a Banks 6 Gun and Monster Exhaust on my '08 LMM, and there is NO discoloration in my exhaust tip. I installed the Banks package in April, and monitor the DPF regens on the optional Palm PDA. I haven't seen more than one or two regens since I installed the Banks package; before that, I have no idea when or if it regened. I have 25K on the truck now. Absolutely stock, one month after I drove it off the showroom floor, I averaged 16.8 mgp from Dana Point, CA to Portland, OR and back. A month later, with a hard bed cover, the same run I averaged 17.2 mpg. With the Banks package, the same run would probably be at least 20, maybe 21 mpg. I run Amsoil SAE 5W-40 Premium API CJ-4 Diesel Oil.
It seems that you gentlemen are both running a programmer. Mine is stock. i thought it was uncommon to see without, but again as James said, it settled in around 25K miles (mine around 20K)...
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Old 11-10-2008, 09:13 PM   #6 (permalink)
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I was positive... now I'm negative for a while...

On my 07.5 2500HD I was getting as good as 22 highway unloaded and 13 pulling 13K 5th wheel.

Now I have a new 08 3500HD DRW and I'm getting 17 highway unloaded and 9 towing. I want to strangle myself. It's actually at the dealer now to look at it. They do not think that's right either. It's also got a few other demons to excise.
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Old 11-11-2008, 08:12 AM   #7 (permalink)
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With 500 miles on the ticker I hooked a 9000lb trailer behind the truck and pulled 1500 miles. I got between 10-11 for the whole trip. When the truck hit 4500 miles, I loaded up the family and filled the bed with our stuff and drove from Santa Maria, CA to Albaquerque, NM. I drove 70-75 the whole way and the fuel mileage stayed constant between 20-21. I am averaging 13.5-14 mpg in the city, I wish that was a little better. Overall though, I am very impressed with mileage of this truck so far. I really want to see what it will do without the DPF, but I am very hesitant at the same time.
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Old 11-11-2008, 08:39 AM   #8 (permalink)
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I just picked up my 08 last saturday and saw 24.9 on the dic yesterday when I was on the interstate on my way into work. Now with a combo of city and interstate driving its reading 20. FYI I don't know how accurate my dic is as I have not filled up and hand calculated it yet.
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Old 11-12-2008, 05:35 PM   #9 (permalink)
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When I set out from Oregon driving down to Cali I was seeing about 18.5 through the Mountains the first day. The second day, once I hit the flat highway I was seeing around 20.5. The truck had about 3,000 miles on her when I set out.

'08 3500 SLT, CC, LB, 4wd, LMM (unloaded)

Tom
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Old 11-12-2008, 10:32 PM   #10 (permalink)
grandpa67
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Let my LMM go until the low fuel warning came on. It took exactly 21 gal full to the neck and I had gone 386 miles so I got just over 18 mpg. That was rural driving w/o a load, very little on level roads. The truck is completely stock with just over 8K on it now and I'm running 65 lbs in the front and 70 lbs in the rear tires. BTW the DIC has been very accurate.

Looks like I have 4 gal left when the warning comes on. I'm happy with the milage so far and it just keeps getting a little better as I put on the miles.
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