Absolutely terrible gas mileage.

[tatca]

Originally Posted by Savington

Just finished my first highway tow and I am seriously considering selling the stupid truck. The truck is an '05, crew cab shortbed, totally stock all the way down to the 245s on stock wheels, towing a 7500lb 26' enclosed car trailer. Doing between 60 and 65mph the entire way, I just averaged 11mpg. My damn 5.3 Suburban can probably beat that. Fresh fuel filter, too (500 miles on it now, NAPA Gold). I am getting MAYBE 14 around town, 17 unloaded on the highway cruising at 70.

What can I do to bump this up, aside from selling it and buying a Cummins? My roommate's '94 Dodge averages 16mpg pulling the same trailer at the same speed.

I have a 2005 crewcab, short bed, 4X4 all stock. my unloaded mileage is 20-22 MPG driving 60-65 in rolling terrain. I tow a 10K-11K pound 5th wheel and average 12MPG driving 60MPH in rolling terrain. In flat interstate conditions, my towing efficiency increases to 14MPG. In mountainous conditions, efficiency deteriorates to 9-11 MPG.

Terrain and wind conditions, as well as your driving style, will have a significant effect on efficiency. You should also check your tire pressure. I operate my truck and 5th wheel at max recommended pressures: 80-psi in trailer and truck rear wheels; 55-psi in truck front tires.

tatca
2005 LLY, crewcab, 4X4, all stock

[New2DMax]

Originally Posted by tatca

I have a 2005 crewcab, short bed, 4X4 all stock. my unloaded mileage is 20-22 MPG driving 60-65 in rolling terrain. I tow a 10K-11K pound 5th wheel and average 12MPG driving 60MPH in rolling terrain. In flat interstate conditions, my towing efficiency increases to 14MPG. In mountainous conditions, efficiency deteriorates to 9-11 MPG.

Terrain and wind conditions, as well as your driving style, will have a significant effect on efficiency. You should also check your tire pressure. I operate my truck and 5th wheel at max recommended pressures: 80-psi in trailer and truck rear wheels; 55-psi in truck front tires.

tatca
2005 LLY, crewcab, 4X4, all stock

My experiences are about the same as this. As a daily driver, mostly short trips (8-20 miles) I am averaging 16.5-17. Stretching out on the freeway hauling just me and family I get 20-21. Towing my 11,000# fifthwheel I have seen as low as 10.5 and as high at 12.5. It is Jayco Eagle so it is basically a square box. Aeordynamics is not really in their design criteria.

I have also hauled a small 6'x10' single axle enclosed trailer, loaded to about 4k. This square box pulled me down to about 14mpg. I feel that what you tow and how you tow it makes all the difference.

All of these numbers are hand calculated. I reset the computer to the new 265s and it matchs my GPS pretty much dead on so I know the numbers are correct. Another thing that pulls down the numbers just a little would be the warm up and cool down times. I don't just pull into a stop and shut it down. I will usually end up stopping at least once per tank for the wife and daughter to get a bathroom break. This means the a/c is running while they are inside to keep my other daughter chill'n in the back.

[bowhunternkbay]

One thing people do not remember is towing a trailer is like draggin a parachute behind your truck!!! Do a few of the small mods and you will see a significant improvement in your mileage.

[bpe1]

Well I for one get poor fuel mileage with my 05. Mb didn't help my mpg at all. Did run better and as long as temps don't get over 90 fan doesn't run a lot. Over 90 is still a big issue with fan. Best yet is 14.8 all interstate running 68 mph unloaded. Pulling my 34 foot rv is 7-8. Truck runs great, no white smoke, no diesel in oil. Just loves fuel. And yes, I still wish I'd got a Cummins. Dodge builds a poor truck in comparison to GM but they get great mpg and are very dependable. I have to admit though, most people who gets poor mpg own an 05 lly. If I came to this forum before buying, I wouldn't have.

[1953drtelco]

I own a 2005 with a LBZ mouthpiece. I'm getting at least 13 mpg (Hand Calculated) towing my boat...approx 6500 lb. I tow at max 65 mph, but my truck still has the stock tires and stock height. On the freeway without towing anything I average over 20 mpg driving at 70 mph plus. I purchased my 05 used and luckily I purchased an extended warranty. The so called great Allison transmission self destructed within 2K miles. At least most of the cost of repairs are covered, and really can't complain since I have no idea how the truck was driven before I purchased it.

[bpe1]

Originally Posted by 1953drtelco

I own a 2005 with a LBZ mouthpiece. I'm getting at least 13 mpg (Hand Calculated) towing my boat...approx 6500 lb. I tow at max 65 mph, but my truck still has the stock tires and stock height. On the freeway without towing anything I average over 20 mpg driving at 70 mph plus. I purchased my 05 used and luckily I purchased an extended warranty. The so called great Allison transmission self destructed within 2K miles. At least most of the cost of repairs are covered, and really can't complain since I have no idea how the truck was driven before I purchased it.

I would suspect you have an aftermarket tune on your ecm. 1, tranny going south, 2, 20 mpg. Never read of a stock lly getting that mileage. Yes with mods, not stock. You could have one and not know it being you bought it used. Dic=lie o meter.

[mijdirtyjeep]

Originally Posted by bpe1

I would suspect you have an aftermarket tune on your ecm. 1, tranny going south, 2, 20 mpg. Never read of a stock lly getting that mileage. Yes with mods, not stock. You could have one and not know it being you bought it used.

X2 on this one, I had one on mine when I bought it and did not know until I tried to load a QuadStealth2 on it (would not work). It took getting EFi live to solve my problem (or at least that is what I told my wife I needed it for)

[New2DMax]

Originally Posted by bowhunternkbay

One thing people do not remember is towing a trailer is like draggin a parachute behind your truck!!! Do a few of the small mods and you will see a significant improvement in your mileage.

What mods are you referring to? Most of what I have read here are mods to bring it back to what the LB7 started out as. (no EGR, no DPF, no Cat)

I also haven't pulled that camper yet this year, since I put on the 4" exhaust, so I don't know how much of an improvement the free flowing exhaust will make. I hope it is alot.

[buckmeister2]

SLO,
though your mileage is not great, it is okay considering that you still have things you can do to improve it. But, two things you said bother me just a bit. first, your 5.3 sub is going to get 9.5 to 10 towing the same rig. I have had 3 subs with 5.7, and 6 z71 trucks with 5.7/5.3. none of them could get over 10 towing 6000 pounds. Second, I will bet you a years braggin rights, right here in front of everyone, that your "roomie" is not gettin' no 16mpg pulling a 7500# trailer, unless he is going downhill, or keepin it under 65 mph on level ground on a cool day. Any of the Big 3 diesels are great rigs for towing heavy loads, and drivers have to have reasonable performance expectations.

[Savington]

Originally Posted by buckmeister2

But, two things you said bother me just a bit. first, your 5.3 sub is going to get 9.5 to 10 towing the same rig. I have had 3 subs with 5.7, and 6 z71 trucks with 5.7/5.3. none of them could get over 10 towing 6000 pounds.

Don't know why. Towing a 5k flatbed, my Suburban would get right about 12mpg, towing half flat half hills at 60-65mph. This is what I would expect out of a new-ish gas motor. The LLY, towing the exact same load (to the pound), on the same terrain, at the same speed, just did 12.9 this past weekend. This is, to put it bluntly, pathetic.

Originally Posted by buckmeister2

Second, I will bet you a years braggin rights, right here in front of everyone, that your "roomie" is not gettin' no 16mpg pulling a 7500# trailer, unless he is going downhill, or keepin it under 65 mph on level ground on a cool day.

He gets 19-20 unloaded. I get 16-17. He gets 13-14 towing a 26' enclosed with a pair of Spec Miatas (10k+lbs), I get 10-11 towing the same trailer with one less Miata. I didn't spend $10k to upgrade from the Suburban, just to turn around and spend another $2500 on a programmer, exhaust, intake, blahblahblah just to match the mileage of other trucks on the market.

Maybe I will just sell it. It's a real shame, too, since it's a nice truck, but I bought it to save money, not to spend it.