Maximizing LLY fuel mileage

[ToddMeister]

This "economy tune" sounds real good.

I think mine would have done about 17 -17.5 driving as you have described.

If true, at $3.00 per Gallon, you saved about $30 on this trip, and if you keep the truck for 200k you might save about $4000.

From what I saw on Kennedy's site, you need a spare ECM to load his tunes.

What was the procedure for you, and what did the whole thing cost???

Check with John Kennedy for current pricing.

There is an article currently on the site that shows how to change the ECM.

Here is link to the article:

http://www.thedieselpage.com/reviews/jkecm2.htm

[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.

[Uncle Wally]

It's been a while since I've posted on this. Figured it was time to do some updating.

I've had a couple hand calc'd tanks of fuel through the truck that were right around 20 mpg. Nothing consistant enough to say it's reliably doing that.

Couple of things I noticed:

Since the mandated Ultra Low Sulfer Diesel, I've noticed mileage drop about 2 mpg.

There weren't any changes with the truck until June when I finally got the Alcoa's with 235/85 16's on. I figured that would increase mileage a mpg or two. It did the exact opposite. I now run 200 rpm less at 55 mph, but mileage dropped. It either has to do with the rolling resistance of the A/T Revo's or the wind resistance due to the 2" wheel spacers between the duals. Not sure yet. I might try to remove the spacers, inflate tire pressures to keep sidewalls from rubbing and give it a go. That should answer that question.

Then in August I had some electrical issues that forced me to reinstall the stock tune. The problem hasn't been fixed yet because the dealer couldn't figure anything out. So the stock tune remains until further notice.

Now I have something leaking fuel somewhere. I can smell it, and it doesn't always start.

Bottom line.....

Fuel mileage the last month has been between 10 and 12, hand calc'd. 57K. New Blizzaks. No load. 10 minute warm up prior to driving. It doesn't get driven nearly as much with these rediculous fuel prices and the lack of decent mileage.

The two monthes prior 13-15.

I sure hope fuel prices correct themselves soon. At a C note to fill it, I'm getting frustrated.

Waldo

[bubbancolo]

Just bought my 2004 3/4HD Duramax longbox and drove from Colorado to California. Using the DIC I got high 18s driving between work and home the first few days prior to trip. Speeds didn't exceed 65 and had stop and go driving some of the way. Once we hit the interstate on our trip we only saw ~17 mpg, lots of hilly grades getting into Wyoming and high head winds. Once we started west bound at 75mph on cruise I got 18.7 mpg, I checked manually and DIC was within .4 mpg of actual. Now once I let the wife drive she set cruise at 80 mph and mpg dropped down to 17.8 mpg.
I filled in Reno and drove up and over Donner Pass and down into Chico speed limit was 65mph on freeway and ended up driving many back roads at 35 - 45 mph, on that tank I got 20.5 mpg. Truck is completely stock and has 26K miles on her. There were 3 adults and two children on board.

Running with my 8.5 foot truck camper (pop-up style) @1600lbs +gear=total of 1800lbs~ and a ATV trailer with two ATVs added another 2200lbs, running back roads and in the mountains taking on several passes and using tow haul mode and keeping my speed no higher than 65mph, my mileage runs about 13.8 mpg.
WOW I love that trans! Makes hills disappear and control in turns great. Oh stopping was much better with trans downshifting for me!

[larryh1]

I am running the Hypertech on my LBZ. I got it after my Chevy dealer told me to get one. I drive it easy for the best gas milage also. The very best I have gotten is 16.5. I am going to a larger exhaust mainly for towing reasons, (the speed shop says it will lower my turbo temp's) but I hope I get some gas mileage out of it also.

My Hypertech has three programs; performance, performance tow, and safe tow. I generally keep it in safe tow because of the trailer I tow, a 30' toy hauler, about 8,000 loaded. I did notice better pulling power right away, but the truck didn't need the extra power. I was hoping for better gas milage, but don't see it. I don't really expect a whole lot of gas mileage towing, but I would like better when I'm not towing.

Can anyone who is familiar with the Hypertech programer tell me if I would get better gas mileage in the performance mode. I haven't run it in that because I'm afraid it runs the motor too close to it limits. I bought the truck planning on keeping it for a very long time and don't want to damage it. I have tried the performance tow ( book says this is for towing items less than 6000 lbs), but didn't see a difference. The trans shifted at different points but the torque and power felt the same.

Any replys would be greatly appreciated.

Larry.

[Fireman Fred]

I recently purchased a 07 Classic 4x4 stock drive train and 285 tires. I get 14+- in the city and 16ish unloaded on the hywy. my camper is 8k and i get 9 to 10 best I recently pulled a boat (9-10k) flat land and got 6mpg is that to be expected? should i be looking for somthing wrong? my speed was approx 68 and 1600 rpms. i had the GM place look at it and they say it is in spec's. she does not struggle at all just poor milage, any thoughts.

[mr. monte]

your 285's are killing you

my '07 classic w/ the LBZ can squeak-out 22 mph unloaded keeping it at 55-60 mph, all stock except for a 4" turbo-back system, EGR block-off, and diesel kleen added to every tank, as soon as you go over 60 mph, mpg drops quick

[JohnC]

Is your odometer corrected for the 285 tires? You may be going more miles and more mph than you think, both of which would make the mileage seem low.

[dannomatt]

Some random thoughts.
My take on the D.I.C.: (Don't) Trust, but verify. Mine is seldomly better than .5 MPG off.
My MPG: 15 - 17, with my best now being 18. (2005 C/C, L/B, 2WD, all stock - except tires - See below)
ULSD: The change-over was before I owned my LLY. But I know that the Cat 3126 in my M/H lost 2 - 4 MPG due to ULSD.
Tire size vs. MPG: I lost 2 - 3 MPG due to the 265/75-16s I installed on my truck. With the 245s, I always got 17 - 19, with the best being 20.8.
'DPS' in Van Nuys, Ca. recommends the 'Predator' hand held programmer that can install/uninstall different tuning maps for power - economy - etc. Customer claims of 1 - 3 MPG.
Regarding above: I'm chicken. Too many horror stories of codes being flashed due to re-programming. (In all fairness, very few ugly stories are about the Predator - But I'm still too anal to experiment)
Dan

[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....