2005 Chevrolet Silverado C/2500 6.6 L V8

I am averaging about 9mpg with a combined weight of around 26K, pulling Fuzion in sig and Sea Doo in tow behind that. This is with my 06 LBZ, but I think it is still related to what you could expect at this weight.

what he said.

I get 11-12 towing at 60- 65 mph. 65 is a sweet spot for those 5 speed LLY trucks. Most trailer tires aren't beyond 65. Mine has never overheated but the fix is relatively simple and cheap.

I average between 10-12 mpg pulling my 12.6k lb. 5th wheel. It's never overheated and usually stays around 190 degrees during normal driving conditions. I have seen it hit 220 pulling a long grade once. The best thing I ever did was install EFI live with the heavy tow tune and turbo brake. The few extra hp made a big difference.

To the OP
I get 12-13mpg with truck in sig (similar to what you are looking at) pulling a fiver that weighs about the same as yours.
Note it is a 2005 LLY. It DID get warm enough for secondary fan to kick in a few times until I had the "GM fix" applied (LBZ aircleaner, which draws cool air from under the fender vs hot air from behind the rad).
Have not heard the secondary fan since.
So don't let the LLY haters scare you off!
Note, my truck is 2WD, which may help 1/2mpg or so.

Turtle n Peeps wrote:
FYI: The 06 LLY never had cooling issues. The 06 LLY was just a detuned LBZ so it had the same mouth piece and radiator as the LBZ.

Thx..couldn't remember...I went from an 05 LLY to the 07.5..sorry about that.

Turtle n Peeps wrote:

Camper 2012 wrote:

Turtle n Peeps wrote:
Year after year I get 12 towing my 28' TT at 70 to 75 MPH with my LBZ. This is over 10's of thousands of miles across the western/ mid western US towing.

I know it would pull down 13+ MPG if I slowed down to 55 or 60 MPH but I don't have that much time on vacation so I tow fast and take the penalty.

Keep in mind that my trailer is old so it's heavy for it's size. I'm around 16K combined gross.

On the highway solo I can get 19/20 and mixed I get 16 and change.

Is your truck 6.6L?

Yes, all Dmax, 2001-2014 2500 & 3500 series pickups are 6.6 liter diesels. All have a 3.73 rear end. 2001-2005 had 5 speed automatics (unless they were a stick) 2006 on up have 6 speed automatics (unless they were sticks).

It's to note that a "few" LLY engines (the engine your looking at) had heating problems. These problems can be fixed with a new turbo mouth piece and/ or a new LBZ radiator.

It's also to note that this engine will get slightly less, (1/4 to 1/2 MPG) and I do mean slightly less fuel mileage than the LBZ engine.

Also my truck is a 4X2 with street tires for maximum mileage. Like I said, these figures are "average" over many years of driving it.

Thank you.

rjstractor wrote:

Camper 2012 wrote:
Is your truck 6.6L?

All Duramax diesel engines in Chevy or GMC pickups are 6.6 liters. There are many variations but all are the same displacement.

Thank you so much.

macsplinter wrote:
I have a 2005 duramax and pulling a 6500# 29' TT I get from 9 to 12 mpg depending on hills.

Thank You so much for your post. Have a nice day.

FYI: The 06 LLY never had cooling issues. The 06 LLY was just a detuned LBZ so it had the same mouth piece and radiator as the LBZ.

Turtle n Peeps wrote:

Camper 2012 wrote:

Turtle n Peeps wrote:
Year after year I get 12 towing my 28' TT at 70 to 75 MPH with my LBZ. This is over 10's of thousands of miles across the western/ mid western US towing.

I know it would pull down 13+ MPG if I slowed down to 55 or 60 MPH but I don't have that much time on vacation so I tow fast and take the penalty.

Keep in mind that my trailer is old so it's heavy for it's size. I'm around 16K combined gross.

On the highway solo I can get 19/20 and mixed I get 16 and change.

Is your truck 6.6L?

Yes, all Dmax, 2001-2014 2500 & 3500 series pickups are 6.6 liter diesels. All have a 3.73 rear end. 2001-2005 had 5 speed automatics (unless they were a stick) 2006 on up have 6 speed automatics (unless they were sticks).

It's to note that a "few" LLY engines (the engine your looking at) had heating problems. These problems can be fixed with a new turbo mouth piece and/ or a new LBZ radiator.

It's also to note that this engine will get slightly less, (1/4 to 1/2 MPG) and I do mean slightly less fuel mileage than the LBZ engine.

Also my truck is a 4X2 with street tires for maximum mileage. Like I said, these figures are "average" over many years of driving it.

Thanks, that is what I was trying to tell him on his other thread as well as this one, but evidently he didn't read them......

Wasn't going to go with LBZ, LML, LLY ect because OP didn't seem to know that the 6.6 WAS /IS the D/A engine. and the 05'-06' LLY did have cooling issues, though I think the 05' was more troublesome than the 06? I had the 05', and only once did I "heat up", but nothing else happened.

I owned quite a few Chevy D/A combo's..that was what I was telling you..I would go to web site: thedieselplace...it's all about Chevy/GM duarmax allisons and each forum covers certain year diesels...You may be able to learn a little more about them and what you want to purchase....The Allison transmission has a grade braking feature that is great.

Dodge??? Where did I say anything about buying a Dodge, you were asking about Chevy 6.6L diesels and I've owned and towed with them and was giving you information on them.