Maximizing LLY fuel mileage

[REDTRUCK05]

After over a year of complaints to my dealer, and many letters to GM about my UGLY MPG, I did get help! The general manager of my dealer I bought my truck from called me in. He had me uninstall my edge system and GAVE me a hypertech! After install I got 20.5 at 70 and 18 city! Keep in mind that these are computer reads and not yet calculated. With my past calcs, the DIC has never been off by more than 1.5 MPG. This would put me at an increase of between 3 and 5 MPG better across the board! I will keep you informed on later calcs.

[rob from bc canada]

I'm sure a lot of us will be waiting to hear further results from that installation.

Not knowing much about these things, I wonder what programming they put on that, that they couldn't put into their own PCM.

[Kennedy]

After over a year of complaints to my dealer, and many letters to GM about my UGLY MPG, I did get help! The general manager of my dealer I bought my truck from called me in. He had me uninstall my edge system and GAVE me a hypertech! After install I got 20.5 at 70 and 18 city! Keep in mind that these are computer reads and not yet calculated. With my past calcs, the DIC has never been off by more than 1.5 MPG. This would put me at an increase of between 3 and 5 MPG better across the board! I will keep you informed on later calcs.

By nature, chips and tuners alter fueling by sliding fuel to the engine under the table. This will cause the DIC to become less accurate in most cases. The severity of this inaccuracy will vary depending on where the changes have been made. The Edge for example, does very little to the cruise fueling and is more of a demand based unit. The Hypertech is not particularly aggressive down low, but could skew the readings. My Economy tunes have varied in their response to DIC calculations. Some have been spot on and others have skewed it. Best is to hand check it.

My Dyno plot shows the power output at full pedal:





Isn't pretty...

[REDTRUCK05]

Because with the hypertech, I have lost the the monitor, can I reinstall my edge along with the hypertech? Is this dangerous?

[Kennedy]

That one you should be OK with, but only because it is an LLY. The LB7 Juice still adds timing.

[AVEX]

What setting is your Hypertech on in order to get the MPG? I have one and mine has worsened. I have tried stage 2 and stage 3, I am going to set stage 1 today. I have had this a week. I like the response and the increase in HP. My DIC says 13.7 but calculated it is more like 12 to 12.5. In either Stage 2 or Stage 3. Without the Hypertech my DIC is accurate. I will post MPG's after I run it in Stage 1 for a couple of days. As far as driving habits go, I do not drive this like a race car. Coast to a stop for minimal use of brakes and ease into accelaration when taking off or merging. Before I took it to the dealer a couple of months ago I was getting 16+ without anything. I want just that back at least. They had to update my #7 injector pigtail. Now I have a couple of codes I will also post that later as well.

[rob from bc canada]

I'm still getting a pretty reliable hand-calced average of 18 US mpg, running unloaded bone-stock about 90% Highway, 10% Local/City driving, with highway speeds of 60-70 mph.

I also drive for mileage, as well as I can, but I can't resist blowing smoke once in a while

The average miles per engine hour is 37-44 over the last few tankfulls.

That is with a 3500 longbed 4x4, weighing in at about 7150-7200 lbs as she sits, with 27,000miles 43000km on the odometer.

[gary_lucas]

I just got a new (to me) 2004.5 Sierra 2500 Diesel.

Truck has 181,000k on it.

We took it for the first trip with the camper on the highway this past weekend.

It looks like I was averaging 15.6 to 16.4 l/100k (15.08 / 14.34 MPG)

Looking at instant fuel economy I could see it was hitting as low as 9l /100k on flat stretches at constant speed. Our trip was only about 70k on the highway at constant speeds, so I expect to see better results when we go to Tacoma (300ish K)

Mileage in town is more like about 17-18l / 100k (13MPG)

It's BC so it's not flat, but it wasn't terribly hilly either, we were towing our TT (3000lbs current weight).

I was not driving as efficiently as I could, we're going to Tacoma in 2 weeks, I think that will be a better test (flatter) and I'll try to keep the lead out of my foot... And the drive is quite a bit longer... So I'll get a better sample...

My truck came with an Edge CTS in it, but it looks like the firmware hasn't been updated for awhile. It's missing the mileage calculator / mileage coach that should be there in theory.

I'm going to bring it upstairs and see if I can get it updated this weekend. I've only used it at level one, which theoretically is a mileage setting.

Any suggestions? Looks like someone already updated the mufflers, there is two giant tailpipes, I'm pretty sure that's not stock.

Thanks all

[AKMark]

I picked up an 05 2500HD CC LB 4x4 this summer. It was used on the north slope oil field of Alaska and has been prepped for extreme weather. The bumpers on it must weigh about 300 lbs a piece. It only has 91K miles on it, it does have over 12000 hours thanks to excessive idling trying to keep the occupants alive when temps dropped below -60.

Love it, TONS of power and does everything I ask of it and more. I had almost 3000lbs in the bed a few weeks ago and the rear suspension wasn't sagging, it was even with the front, but not sagging. The traction like that was amazing.

Pulling a Dead 6.0L Powerstroke she out accelerates my 6.5 empty.

I have a 13-15 mile commute everyday depending on which entry point to the Army base I have to use. I averaged 15-16 doing this run every day this summer. It dropped a little when I was pulling, but not much.

I haven't had a chance to take her on a longer drive to see what it does when it runs a full tank of fuel without having to warm the engine up multiple times. With it being -30 now and running it a little more than normal mileage is still 14, which is better than the old 6.5 did.

The 6.5 Burb got 14 in the summer doing the same run and about 12 in the winter. On the Hwy the Burb pulls close around 18-19 empty and about 13 pulling a K-5 on 1 tons and 36's.

Would love to find a way to get into the 20's, but my 235/85's probably aren't helping. I'll live with the lower mpg's to run these tires. Oh and I hand Calculate my mileage from a Garmin GPS, as both the Burb and Truck's speedo's are slightly off thanks to the tires.

[Kennedy]

The 235's actually should help. Decent height and narrow. The heavy bumpers certainly do not help, but I'm sure they'll come in handy if wildlife is standing in the road.

[AKMark]

Wildlife or the occasional vehicle that decides to cross my path....