I just got back from my first towing trip with my 05 sierra. I have mixed emotions. I have a 14' gooseneck horse trailer and a Predator set on 40 hp. The trailer probably does not weigh in at more than 3000#. I can't even tell it is back there. The truck has all kinds of power. It never downshifted on the whole trip (Alabama to Oklahoma and back) of course there are no real hills to speak of. So, performance-wise I cannot be happier. But fuel mileage? -:t . Going out there with an empty trailer (except saddles and such), driving the posted speed limits (boy that was hard to do :lol: ), I only got 11.4 mpg -:t hand calculated. I was in a headwind the whole way, but I was still dissapointed. On the way back I had a 1000# horse on the trailer drove 70-73 mph without a headwind and still only got 12.4 mpg. What gives? My '99 6.0 gasser would do almost as good (10.5-11 mpg) on the same trip and my '02 LB7 would do 13.5-14 mpg, bone stock. Anything I can do to improve these numbers? Can I expect better? BTW I have abot 7500 miles on the truck.

With fuel up over $2 a gallon this can get expensive.

I hear you! I towed a 7500lb TT this weekend and got around 10mpg. Still better than my 6.0 gasser, it got around 6.5mpg.

Cowdoc -


How many miles do you have on your Sierra? Once you reach about 10K miles, or so, you should see a jump in mileage (at least I did anyway with LB7).

The jump consisted of about 2.0 to 2.5 MPG...
:sheephump This emoticon is not really applicable, but it is hilarious!!!!

BTW I have about 7500 miles on the truck.
he says..

cowdoc- How were your egt's? The Predator runs a little hot so anything that can be done to help evacuate the extra heat will help out. Looking at your sig, it looks like you have a stock exhaust system. I would look into a 4" cat-back system to replace it. This will help out quite a bit.

cowdoc- How were your egt's? The Predator runs a little hot so anything that can be done to help evacuate the extra heat will help out. Looking at your sig, it looks like you have a stock exhaust system. I would look into a 4" cat-back system to replace it. This will help out quite a bit.
I do not have guages yet, but I didn't think I had to worry too much about egt's on 40 hp setting and such little weight. I do plan on getting guages as soon as I get the $$$$! Will excess heat lower mpg? Should egt be a problem under the conditions I described?

I too have mixed emotions. On the two tows I've done with my 8K dry toyhauler I've been down at 9.5 according to the DIC, so probably more like 9. This was on some decent grades (9+ %) here in AZ, but even on level ground at 65, a reset of the CPU still averaged 10 mpg.

My Cummins usually got around 13, with 11 being the lowest.

I'm really not holding my breath for any bump as I get more miles either. If the rings haven't seated by now, I doubt they ever will.

cowdoc- Im sure you were fine temp wise, but remember, the LLY's run HOT stock. Anything you can do to open up the exhaust will help get rid of the excess heat created by the programmer and you will run much cooler. This in turn will help your motor run much more efficient. 4" exhaust is the first mod I recommend to people w/LLY's even if they arent going with a chip/programmer.

Hmmmmmmmmmm. I can't figure out why some people have such crappy mileage. I just towed my ole Camaro from FL to MS.... about 400 miles one way. Pulling 5500 # I got almost 16 mpg. Coming back empty I hit 20 for the first time. Truck has 8000 miles. Mods are Hypertech on level 2, flowmaster muff in place of factory muff and a K&N installed in original modified air box. Couldn't be happier with this truck.

Hals, was that MPG figured by hand or with your DIC? :lol: Remember, the DIC is generally optomistic to begin with, add a programer to it, and it can be WAY off.

Hope this pic comes out OK, as I know my trailer is a bit of a brick wall. I now have a shell on the back of the bed, but it made zero difference.

Again, this thing clocks in at 8300# empty. Add 100 gallons of water and 36 of fuel, plus gear and what is in the Sierra, it isn't trivial, but the Cummins still did a bit better...

http://ww2.leamonland.com:91/photogallery/NewYears_05/images/DSCN4760.jpg

That was hand calculated. The DIC was reading 23.6 on the 20 MPG leg. I tow the Camaro to the track often and had never gotten worse than 15 with 4 people and a bed full of tools and equipment. It just seems that some people get great mileage and others get crappy. I know that my truck will get better mileage with the Hypertech removed... so.......

And you are measuring the distance with a GPS or a odometer that has been calibrated? Getting 20+ empty with any of the big 3 diesels today is fairly doubtful IMHO. If you are, that sure is great for you though!

I will get 17.8-18 mpg all day long hand calc. @ 70-75 mph.
Towing my 5er about 12mpg. it seem even on the stock setting of the Edge I loose about 1.3 mpg -:t

And you are measuring the distance with a GPS or a odometer that has been calibrated? Getting 20+ empty with any of the big 3 diesels today is fairly doubtful IMHO. If you are, that sure is great for you though!

I average 20+ MPG empty. When pulling a 7000 lb TT I average 12-15 MPG. These numbers are without the tunes installed.

Lots of people are getting 20+ mpg out of their trucks. I don't have GPS or a certified speedo. The trip I take I've traveled many times in several different vehicles. Not to mention my family and in-laws make the same trip. It's always within 10 miles difference. I'm not suprised that I got 20 mpg, only that it happened with the Hypertech set on 2. That's what suprised me............... Great mileage and power too!!

Just got back from first RV trip with Banks 6 gun. All of my empty driving, I get better MPG on stock setting, even driving conservative, around 18-20 MPG. On this trip pulling about 15K we got 11 one way and 10.7 coming back on a 320 mile round trip. The most I ever got going on this same trip before is 10.3 and as bad as 9.5. It seems empty the banks uses more fuel, but loaded and needing the extra torque it even gives a little better.

I really love the towing uphill difference and take offs with the Banks. I will only go to level 3 with this load, as not to ever hurt anything. This was money well spent since I wanted it for the towing to begin with.

I got 18.4 running empty hand calculated with the predator set on kill. I don't do this on a regular basis but I wanted to see if this tune would kill fuel mileage.....328 highway miles. Cruise set at 75 most of the way. I do get better mileage with the truck set at stock and the edge even set on 0 made mileage worse in the past. I can get 20 mpg fairly consistently with no tuner and cruising at 75 on the highway.

I'm still under 500 miles on my new 05 and the DIC is just starting to read in the 12 point somethings. It started out in the 10's. I haven't been too concerned because of what I've read here from the guys. I'll just be patient and let her wear in and settle down before I get serious about reading MPG's. I'm sure it will crawl up as time goes by.

Nice trucks aren't they.

I'm wondering the same thing that hals73 is: I haul a 10000 lb trailer in Oregons cascade and coastal mountains and get on average of 12.8 to 13.4 mpg depending on how lead footed I am at the time. Maybe because it's just a stock LLY motor with no aftermarket parts?

Just a quick reminder, GOOD FUEL makes a BIG differance with a Diesel on fuel milage and power.

Montana Mike..........very true.

Summer fuel will certainly increase MPG when the switch is finally made here in Michigan. Winter blends in Northern states reduce performance and MPG.