Maximizing LLY fuel mileage

[Uncle Wally]

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]

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]

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]

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]

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]

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]

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