Maximizing LLY fuel mileage [Archive] - TheDieselPage.com Forums

Stlheadake

05-17-2006, 11:32

I am new to this forum, and I have to admit new to Diesels.

My father had had his '93 6.2 since 95. It has been and continues to be a great truck. He is consistently getting 22-24 MPG HWY running 70MPH.

I have an '06 crew cab 4x4 with only a thousand miles on it. I have the LLY motor (darn it!), and it is bone stock. The only change or addition is a Line-X spray in Bedliner. I have stock wheels and Tires, no bug deflector or ANY changes to the truck. So far, I haven't gotten better than 16 unloaded on the interstate at 65MPH. I think I am running the 3.73 gears in the rear, but I don't know how to tell for sure (can anyone tell me how to tell?).

I am sure that as the motor breaks in that I can expect it to get a 'little' better. What is 'average' for most LLY users? I have read several threads, and mine seems low.

I bought the truck for the power, and pulling. But, the MPGs attracted me too. Now I'm not really seeing them. Sorry for being so long winded, but this brings me to my real question.

Would the addition of an exhaust system and possibly a cold air intake increase my mileage? The added horsepower would be good, but I am most concerned about mileage. Also, I pull my 6K travel trailer a couple of times a month. So towing mileage is sort of a consideration too.

I am sort of a MPG nut, and would like to see a little better than 16. My 1/2 ton Chevy with 5.3 gasser got 18 MPG REGULARLY at 70-75 on the interstate (Really!)

More Power

05-17-2006, 12:22

Hi Scott,

You've asked an important question, regarding fuel economy, and your truck's apparent lack of it.

First, all Duramax equipped 2500HD/3500 series trucks come with 3.73 differential gearing. The new 6-speed Allison with its double-overdrive will produce engine rpms roughly equivalent to a 5-speed Allison equipped truck with 3.42 gears. I assume you're running in 6th gear while on the Interstate.

The thread we began a few weeks ago describing a Scatter Plot (http://www.thedieselpageforums.com/tdpforum/showthread.php?t=22302) would be a good place to begin when troubleshooting a low mpg truck. This requires an EGT gauge, and it might be worth installing as a first step (along with a boost pressure gauge). (Read the whole scatter plot thread - to get most out of it.)

We have a pretty good understanding of the relationship between EGT, boost pressure and fuel economy. It requires burning a certain amount of fuel to achieve a given speed. Exceptionally low mpg's must mean either your truck is producing higher than normal drag or the engine/drivetrain isn't running efficiently. Again, an EGT/Boost gauge would show that.

For example, a low boost pressure (due to some turbo or turbo control issue) would cause higher than normal EGT's and allow the truck to produce more smoke. You'll see this immediately with gauges.

IMO - The 2006 LBZ ought to be 20 or better when driven unloaded at 65-mph.

Jim

StrangeEngine

05-17-2006, 12:22

I have an '06 crew cab 4x4 with only a thousand miles on it. I have the LLY motor (darn it!), and it is bone stock. The only change or addition is a Line-X spray in Bedliner. I have stock wheels and Tires, no bug deflector or ANY changes to the truck. So far, I haven't gotten better than 16 unloaded on the interstate at 65MPH.

In spite of a billion posts to the contrary, that's exactly the mileage I see with my '02 LB7 truck and have since Day 1.

I got ONE tank at 20.02 but I had the cruise locked at 55mph as a test. It ain't worth it.

I just don't see how other people are getting 18-20mpg at 70mph in the same truck as I have.

I think I am running the 3.73 gears in the rear, but I don't know how to tell for sure (can anyone tell me how to tell?).

You've got the 3.73 gears because that's all the diesel truck is available with. :)

- Mark

rob from bc canada

05-17-2006, 12:28

Is it a Dually? (I think most use DRW in their sig for that), and is it a 3500?

These add wind resistance and weight.

Also, do you not have the higher ratio 6th speed overdrive tranny? If so you should be getting better than my 05

Is your mileage calculated from ODO readings and tank fills, or is that what the DIC says? My DIC is always 1-2 mpg optimistic.

In any case that mileage seems quite low, unless you're climbing a lot of hills at 65. I find with the weight of these things, they really suck up the fuel on hills.

Driving empty with mine (also bone stock) I get calculated averages of 17.5 US mpg driving mostly highway at 60-65 (with quite a few traficc lights), some local driving, and some medium hills mixed in. I record every fillup I put in it.

This has not changed for better or for worse that i can see since new, I now have about 8000 miles on it.

On straight flat highway at 65 I can get around 18.5-19 US MPG

WILLYD-MAX

05-17-2006, 14:36

Don't expect to much better until you get more like 5k to 10 k on the odo. These duramaxes take a while to break in depending on your use. I drove about 2.5 tankfulls here a while back strictly highway and I averaged 18.8. And that was hand calculated with adding 2.5% for my 265s. BUT I tried to keep it at or under 2k rpms. I don't think people are going to see a drastic differance in the 6 speed ali fuel mileage at lower speeds... rpms. compared to the 5 speed ali. I also think using a good fuel injector cleaner as in FPPF Total Power on every tank helps mileage approx. 1 mpg. Just my experience with my 05....

Stlheadake

05-17-2006, 14:52

Thanks for all the replies. I WILL jump in and read ALL on the scatter plot thread. I DO have the 6spd Alli, and I DO run in overdrive. The truck is a 3/4 ton not a dually.

I just bought a case of stanadyne blue label cleaner, demulsifyer, lube, cetone, etc... I wonder what difference that will make. I haven't used it yet, I am waiting on the O'Reilly cetan booster and lube I used to run through.

I DON'T have a heavy foot, I run 70 mph unloaded and I take my time getting up there. So my mileage seems quite low to me. In all fairness though, I have not hand calculated what I am getting. I am relying solely on the DIC. This may be faulty.

So back to my ORIGINAL question: Will adding an exhaust and intake kit improve milage? I have read where some guys have even put in a performance chip and gotten as much as 5mpg (they claim) better than stock. Is this really true?

It seems that modification would pay for itself in about a years time!

I wanted thoughts from the experts before I plunk down the coin for the toys.

More Power

05-17-2006, 14:59

Stlheadake

05-17-2006, 18:15

By all means, hand calculate the mileage. Try to use the same pump, and use the pump the same way each fillup. I normally just set the pump on the middle speed setting, and remove the nozzle once it kicks off.

A larger exhaust system and free-flowing muffler can have a small effect on fuel economy - but not the 3-4 mpg you're looking for. I'd get gauges first.... :)

Jim

Thanks Jim, you and everyone else on this page are a true asset. I am going to order the guage kit from Kennedy first I guess. Othere than the pyrometer and boost, is there something IN a gauge that I should be looking for?

More Power

05-17-2006, 22:10

Gauge brand, model and mounting location are largely personal choices.

Have a look at the 2005 Gauge Update (http://www.thedieselpage.com/reviews/gauges2005.htm) to get an overview of what's available for conventional gauges and what sort of mounting appeals to you.

Personally, I like the dual gauge pillar pod for boost/EGT, mainly for visibility - and they look cool there. The Edge Attitude (http://www.thedieselpage.com/reviews/attitude.htm) comes in a close second, though I don't know about 2006 model year requirements. The vendors will know.... :)

Jim

David Proske

05-18-2006, 06:15

My 2003 and now my 2006 seem to be pretty close in terms of mpg. From what i've seen driving diesels for a number of years.... anyone claiming 20's at 70-75 is flat out fibbing. Or they are going downhill with a tailwind.

beeler

05-18-2006, 07:25

I have to agree with David. The only way I could get 20 mpg out of my '02 is if I drive like I'm following old folks to church. On long trips on flat ground with no wind and cruise on 75 I get about 19. Most of the time 17-18. Less in the wind or if I'm in a hurry.

I have the Edge box and a 4" exhaust. I can't say that they really made much difference in economy. Maybe a little. Towing milage is better than stock if you pull the hills at the speed you would have stock.

Gizmo

05-24-2006, 13:14

The cost of fuel has modified my driving a bit. Last weekend a 700 mile trip was done mostly with cruise control and 65 mph (slower than I usually drive). The tonneau cover was in place as a couple of threads suggest this does better than my tailgate down theory. A calculated 21 mpg was about 3 mpg better than my normal (lightly loaded (weight) and standard drag profile) . Lower speed and tonneau did make a difference.

Gizmo
2002, 2500HD, 4wd, extended
Stock Duramax/5 speed Allison

REDTRUCK05

05-30-2006, 22:07

jharden1

05-31-2006, 13:02

'04 1/2 LLY/Allison 4Door short bed. First tank got 17.4 MPG. I now have 32k on the odometer. 42 miles each way to work. I run 68-70 on the cruise control. 19.4 calculated last tank. Tire pressure 60 all 4 wheels except when towing, then 80 on the rear.

8000# travel trailer, 4 adults in truck 500# in bed, 11.3 calculated at 65-70 on cruise, in west Pa.

After initial breakin in I averaged 18.4. I recently had EMC reflashed due to smoke at idle. Fuel mileage is up a little, say .2mpg.

Mark Rinker

05-31-2006, 13:46

Also, I would hand calculate your fuel mileage as a longterm average over weeks and months, not single tankfuls. A spreadsheet is a great way to do this. Just a moments worth of data entry, or enter the information off your fuel card statement each month. My Holiday and Shell cards record mileage at the pump at the fillup, so its really easy to do by the month. I know when a particular trucks performance has changed, usually a dirty air filter is to blame.

You'll soon settle into a number that will be noticable when you change something like intake/exhaust, etc. When you complete the mod, start another longterm average over a number of weeks and tankfuls. Then and only then will you know if you have truly picked up a solid increase in MPG.

Finman

06-01-2006, 12:18

I ran a trip Minnesota to Kentucky. A hair under 1900 miles all freeway cruse on 70-75mph. I have a Hypertech tuner and ran it in stage 3. 17.4 MPG hand calculated. Not impressed. Would have got 21-22 with my 02. Black smoke when you put the wood to it and alot of it. Anyone have any thoughts on that? Does not seem to smoke when running in stock.

Mark Rinker

06-01-2006, 14:55

My Hypertech tuner is great at adding fuel (power) but not so great at adding enough boost to burn all that extra fuel (black smoke).

If I were running down the road unloaded and wanted max mileage, I'd either add enough boost to burn the extra fuel, or return the truck to stock settings for the trip.

Your speed of 70-75 has alot to do with it. In fact, I'm a bit suprised that your LLY did that well!

Next trip try stock settings and see how you do, or call JK and add a BoostStick and enjoy the extra (although probably unused) power...

ToddMeister

06-02-2006, 04:20

This past winter I made some trips to snowmobile and got 20mpg at 70 mph hand calculated (on winterized fuel, too). I filled up the truck, hit the expressway, drove a couple hundred miles to our destination, and filled truck up. I did this 3 or 4 times. No fibbing here...

My 2003 and now my 2006 seem to be pretty close in terms of mpg. From what i've seen driving diesels for a number of years.... anyone claiming 20's at 70-75 is flat out fibbing. Or they are going downhill with a tailwind.

Kennedy

06-02-2006, 06:42

I can't get 20's at 70 mph, but at 60-ish mph I can run solidly into the 20's. It will be interesting to see what Uncle Wally reports as I just sent him a tune for his dually. The DIC shows encouraging results so far, just need to hand check to verify...

Uncle Wally

06-02-2006, 10:31

Just to give a comparison as to what my fuel mileage was before John's tune.

05 LLY Crew Cab Dually - stock tires.

Loaded - light to moderate

Modifications at the time were John's 4" exhaust, Uni Air Filter, Mega Filter and Lift Pump/Fuel Pump Pickup mods. I had EFI Live at the time, but chose to leave the stock tune in it for a while.

I was pulling a two place snowmobile trailer with two snowmobiles on it and I had one snowmobile in the bed. There were three of us and our gear in the truck. We added two honda three wheelers to the trailer on the way back.

I drove from Minneapolis to Island Park Idaho in March this year. Temperatures were in the mid 40's for most of the trip out and in the low 60's for most of the trip back.

My best fuel mileage per tank - hand calculated - was 12.5. That was treating the throttle like an egg, using cruise at 60 and never letting the tack go over 2000 rpm.

My worst fuel mileage per tank - hand calculated - was 10. My personal belief is that I got a batch of marginal fuel. I didn't change my driving style much, so I don't know of any other explanation.

Unloaded - with tonneau cover - EFI Live now installed - only changes to the tune were to EGR controls. No added fuel, no altered timing.

I get my best mileage at 50-52 mph. Treating the throttle like an egg, never letting the tack over 2000 rpm even on acceleration. I can get between 16 and 18 mpg. I drove this entire tank of fuel - no wife variables on this one.

I usually don't drive that way day to day, nor does my wife. Normal driving yields a pretty consistant 14-15 mpg.

The only issue is that I spoiled my wife with the new truck, and she won't drive our gas miser car anymore. My wife drives totally different than I do even with me giving her constant grief. Her fuel miser skills have gotten better, but are still not at my level. She only understands two pedal postions: foot completely off the pedal, and the pedal all the way to floor (for both foot feed and brake pedals). With that said, it's hard to get a good fuel economy run when my wife drives. I will work on that when we head to Pittsburgh in July. That way I can actually show her what I am talking about.

Sorry for the long post, but I thought it would be good for a comparison. I installed John's tune yesterday and drove about 45 miles on it. Fuel mileage on the DIC was astonishing. I won't give numbers at this point as I need to hand calc it. You'll here from me after a couple tanks of fuel.

Waldo

Kennedy

06-02-2006, 11:27

Just FYI, the changes made should not have had a big impact on DIC readings, in fact, should be none at all...

JoeyD

06-02-2006, 14:15

Easy driving is key to higher milage. I have not done any highway only trips in my Express but I average 17.5 all the time. I keep speed under 70 on the highway and take off easy in town.
I would think 20 is possible on the highway is you keep it under 70. With the 6spd ally you guys in the 06's run maybe better

REDTRUCK05

06-12-2006, 23:22

REDTRUCK05

06-29-2006, 22:12

Are you happy getting 14-15 under normal driving conditions? U say your best milage is at 50-60 mph? That makes sense, its logic. People just dont drive that slow on the interstate in Mpls. I like to drive the speed limit 70 mph. If I do this I get between 9 and 11 mpg, pulling 5600 lbs. If I treat the pedal " like an egg shell" unloaded I can get 14 - 15 at 70 mph. If i slow it down to 60 mph ( only when I have to ) I can get 16 - 17 mpg. Do you guys really think these numbers are ok? I think not...

Kennedy

06-30-2006, 06:05

Let us all know how ur new tunes do. Why is your 05 for sale?

I'm waiting for more feedback from my testers. I started another tester at the Rendezvous.

I'm not really pressing to sell my 2005, but I put it up in anticipation of acquiring a 2006 LBZ.

I expect 19-20+ mpg from a single rear wheel truck driven at approx 60mph. My MPG drops at 70, but seems to drop less with tuning.

ToddMeister

07-01-2006, 05:21

I'm the economy tune tester from the Rendezvous John was talking about above. Took a long trip this past week and averaged 20 mpg with expressway 70-75 mph, some highway at 55-60 mph, and a bit of city driving mixed in. Outside temps were 75-80 degrees.

Truck is a 2005 GMC Crew Cab 4x4 Duramax LLY/Allison. Presently 13,000 miles on the truck.

I want to take a trip of primarily 55-60mph highway driving to see what the tune is capable of.

I am also running Michelin LTX M/S 265-75-16 tires, which will lower your mileage a tad bit from the stock 245's.

At 70-75 mph EGT runs 600-650 degrees, and boost is about 3.5 lbs (on flat roads). At 55-60 mph EGT is 550-600 degrees and boost is less than 2 lbs. These readings are taken pre-turbo.

More to come....

Todd

Uncle Wally

07-05-2006, 16:33

John - thanks for the reminder. I'm still out of state so there is more to come.

Initial reports thus far:

I weighed or entire rig at the local feed lot as we were leaving: 20500 lbs.

1st tank w/ DIC (no hand calcs at this time) - 13.6 mpg (the wife drove)
2nd tank w/ DIC - 15.8 mpg (I drove)
3rd tank w/DIC - 14.5 mpg (we both drove) This tank also had some some really steep grade coming through Wheeling, EV and then into PA south of Pittsburgh (all hills).

To come:
Hand calcs to compare against DIC (although I did notice less of a discrepancy with the 'fuel used' portion of the DIC).
Empty tank mileage with only me driving
Complete rundown of performance and mileage when I get back home

Just a quick note. Thanks.

Waldo

Uncle Wally

08-08-2006, 23:04

OK. Sorry for the wait. Taking 3 weeks off makes for alot of catching up to do.

Hand calcs are as follows:
Tank #1 - 13.55 mpg - DIC showed 13.6
Tank #2 - 13.65 mpg - DIC showed 15.8
Tank #3 - 12.84 mpg - DIC showed 14.5
Tank #4 - 22.36 mpg - DIC showed 23.6
Tank #5 - 16.16 mpg - DIC showed 18.3
Tank #6 - 13.15 mpg - DIC showed 13.9
Tank #7 - 12.29 mog - DIC showed 13.3
Tank #8 - 11.58 mpg - DIC showed 12.2
Tank #9 - 12.04 mpg - DIC showed 13.1

Again - I fill the truck the same way every time: fuel is at the lip and almost ready to spill out with the truck sitting as level as possible - engine not running.

I compared these figures to hand calcs from date of purchase. They are as follows:

Bone Stock - average of 13.91 mpg over ~10k

With JK's exhaust, Uni Filter and Mega filter upgrades - average of 13.72 over ~7k

Add EFI Live to above (only EGR fooled with - no added fuel or timing) - average of 15.9 over ~3k

Add JK's timing tune to above - average of 14.9 over ~5k (this is skewed as a majority of this is towing our horse trailer - only about 1500 miles without the trailer)

The shining star thus far: I hand calced a tank of fuel at 22.36 on a trip from Pittsburgh to Baltimore and back. This was my one chance to use an entire tank without my wife's heavy footed influence (which ever peddle she has her foot on, it goes to the floor). I only stopped once and that was to pull into my buddies driveway. I drove like a grandpa (no offense intended) and treated the throttle like an egg, never going above 55 mph, and coasting to stop signs and lights whenever possible. I know everyone doesn't drive this way normally, but I wanted to know what the truck was capable of. I usually drive this way when I just filled up the tank and am pissed about how much it just cost me. After a few hours, I'm back to my normal style that yields about 18.5-19.5 on the DIC. I usually get impatient with drivers that shouldn't be on the road, so there are a few full throttle runs and the occasional 80+ mph flights. With that said, I'm tickled to death that a 4dr dually can get this kind of mileage and have the power to play around every now and again.

Had I to do it over again, I would have done the same mods within the first 100 miles of ownership, and I still have a couple to go as of yet.

I keep some pretty decent records, so I would expect an update by the end of summer.

Waldo

Albee

08-09-2006, 19:37

I had a 02 LB7 2500HD W/Allison. Took a trip back to Missouri from Wyoming. From Cheyenne to Lincoln Ne. the truck got 20.7 MPG (hand calculated) running 75 the whole way. On the way back to Wy. the truck got 18.3. Here we go with uphill and downhill and wind. The wind always blows here and alway from West to east. I was very happy. The truck got consistent 15.5 to 16.5 running my day to day routes in town during the summer months. During the winter months it would get right at 14-15 MPG.

The new 06 LLY 3500 Dually, Allison does not do as well. I have not taken the trip back east since had this truck. But running my standard routes here in town the truck gets 13-14 in the summer and in the winter it drops to 12. I now pull a 18K fifth wheel with the truck and pull at 60-65 MPH average. Pull 175 miles to camp over three passes going as high as 9800ft. elevation and the average for the trip is 9.3 there and back. I use much more going than coming home. These were all bone stock truck numbers. I have now added 4" catback exhaust. But do not see much difference, maybe .5 MPG improvement at most. This truck does not do as well as the other one. But as stated before it is heavier and has the extra wheels. But she sure do run good!!

This is a great forum!!!! Keep up the good work guys.

Kennedy

08-10-2006, 06:51

Wow 22+ on a dually! I never figured we'd see a dually cross 20mpg. I've been right around 20 with my single wheel, and recently hit 22mpg. Just need to "back it up" a few times...

Kelly T

08-10-2006, 17:13

Updated - over 25,000 miles now. 19 MPG seems to be working. Bone stock. 2500 HD CC.

http://home.columbus.rr.com/vfrket/Diesel/Diesel.xls

Note my calculated Miles Per Hour (miles for the tank divided by elapsed time (hours) from the from the DIC) to the far right. BTW, I still like my spreadsheet. There are few rows of data where I had to add a couple tanks together.

Kelly

Uncle Wally

08-12-2006, 12:44

John,

I agree with you. I never thought I would see it either.

Did you have the AC on? I've found that makes a pretty significant difference. Although I will have to admit, it's kind of hard to not run the AC when it's 80+ and humid. Ventshades work pretty good with the windows cracked and the vent on.

I also had the tires inflated to max rating in the rear due to the trailer towing.

I want to try running 235/85's and see if it makes a difference. I have a set off my 94 that's begging to be installed. I just need to use up the ones that are on it now. Just wish I didn't have to machine the Alcoa's to get em to fit.

I'm going to be making a run to Eagle River WI here soon. Hopefully I can back up that 20+ number.

Waldo

rob from bc canada

08-12-2006, 13:50

Kelly T:

I looked at you spreadsheet, and you seem to have a period where your were getting 16-17, and then back up near 19 average. Are these all long trip flatland driving - your average speed per engine hour is about same as mine, or maybe a bit higher.

That is pretty impressive mileage - what did you do different?

Bet I can do with careful driving over a tankful is about 18 US mpg.

However mine is a K3500 = 7000 lbs empty and 4wd, is your perhap 2wd, and less weight, which could make a difference?

Kelly T

08-12-2006, 18:09

Best I can attribute it to is crappy gas in the winter, bad road conditions (some time in 4wd just to commute to work), and maybe some more city driving. My 2500 HD is a 4wd. I live in central Ohio so now and then we get some winter. At the time I was disappointed too.

Behavior-wise - biggest thing is trying not to be hard on the gas in stop/go traffice trying to get out of Columbus when trying to reach the highway. That seems to be the killer on calc and indicated MPG quickest. Sometimes when sitting in traffic (red light, grid-lock) I'll shift to neutral (automatic) so the truck isn't pushing against the brakes. My driving has some hills on it, but not a lot.

I have no bed cover either. I'd like a "Undercover" and an Edge Juice w/Attitude (or maybe a visit to John Kennedy) to see how they play out from an economy viewpoint (and some pep when desired). And then a 4" exhaust (full). I don't do anything wild with air pressure - keep it at the top of the normal limit (50 psi). Not hauling a load too often - when I am it is an morotcycle or 4 wheeler and my milage gets better as it keeps air off the tailgate (or seems too).

2 cents,
Kelly

AlbertaDiesel

08-14-2006, 11:31

Hi guys
New here, love the forum so far.
I recently bought an '06 Chev Crew 1 ton SRW LB 4x4 LBZ. My first hand calculation of mileage running empty at average 70mph was 18.32 US MPG. My next was a long trip pulling my 26 foot holiday trailer (which my wife likes to load to the nuts) again at average 70 mph and I hand calculated 10.41 US MPG. Not quite as good as my old '93 Dodge Cummins, but then she couldn't pull that rig at 70 mph all the way, either. I am a mileage buff, too, so I will likely post more results as time passes. With fuel prices skyrocketing lately, good mileage is a big concern. I think a 2 mpg increase would be worth it to justify a "mod".

rob from bc canada

08-14-2006, 15:32

I'm waiting for more feedback from my testers. I started another tester at the Rendezvous.
...
I expect 19-20+ mpg from a single rear wheel truck driven at approx 60mph. My MPG drops at 70, but seems to drop less with tuning.

This "Economy Tune" for sale yet? What is involved and how much?

Need any Canadian testers??? :D

I've got about 17,000 km on my truck now, and I've kept records for every fillup so far.

Kennedy

08-14-2006, 20:59

The tunes are available any time. There is a review by Todd Smith on this site.

sb359

08-17-2006, 10:16

best i've done is 20.1 mpg empty and 15 mpg pulling a 6800lb travel trailer

ToddMeister

09-12-2006, 11:14

Recently took a long trip to the East Coast over Labor Day holiday about 1500 miles, 90% turnpike/expressway driving 60-70 mph, 10% city driving. Truck had 4 passengers, box full of luggage/cargo. I averaged 19.8 mpg hand calculated, DIC said 19.7 mpg average. I'm am running Kennedy's economy tune from the Rendezvous. And also running LT265 tires, speedo is accurate (verified with GPS). Had lots of driving in the rain and wind!!!!

rob from bc canada

09-12-2006, 12:18

ToddMeister

09-14-2006, 10:10

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

09-19-2006, 21:01

rob from bc canada

09-20-2006, 12:10

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

09-21-2006, 06:53

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:

http://www.kennedydiesel.com/photogal/images/Hypertech-LLY-plot.gif

Isn't pretty...

REDTRUCK05

09-21-2006, 18:01

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

Kennedy

09-22-2006, 06:19

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

AVEX

12-05-2007, 08:03

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

12-13-2007, 17:07

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 :D

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

12-15-2007, 00:38

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

06-04-2008, 07:23

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

06-06-2008, 06:53

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

10-09-2008, 11:57

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:confused: 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

10-09-2008, 16:43

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

10-10-2008, 13:39

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

08-08-2010, 08:35

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:mad:.
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:D.
'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:eek:)
Dan

gary_lucas

05-22-2012, 20:40

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

11-28-2012, 10:49

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.