Winter fuel and cold weather use also gets a lot less mileage.
We have a dually and that is just poor mileage not because of 4 tires in the rear.
2001 35 ft avalon alpenlite RK
2005 3500 2wd duramax CC dually
trailair center point suspension
JT Strong Arm Stabilizers
KSH 55 inbed fuel tank
Induction Overhaul Kit
TST tire monitors
You might try Lucas injector cleaner first as it does not contain solvents to clean the injectors unlike some other additives. Maybe start driving it harder also. These diesels weren't made for nuns No disrespect
I have a 2005 LLY. I get better mileage than that towing my fiver (12.5 - 13mpg)!
Consistently get 20 mpg highway at 70mph not towing.
I think you have bigger issues than 2 extra wheels.
FWIW, these are NOT the LB7 injectors that caused major issue on the early D'Maxes (up to 2004 1/2) so I'd be surprised it you have an injector problem.
And the larger turbo mouthpiece is not going to fix your mileage, it helps the engine breathe better when working hard and may help keep operating temps down a little. That and the air cleaner from a 2006 LBZ are the standard fix for the few LLYs that do overheat.
I suggest it's time for some professional diagnostic help.
* This post was
edited 05/04/12 07:48pm by kaydeejay *
1999 Sunnybrook 27RKFS Fiver.
2005 GMC Sierra 2500HD CC/SB/DA 2WD, LLY with LBZ air cleaner, 52 gal Titan tank, Bilsteins, Line-X, Westin steps, Prodigy, Retrax cover, 16K Superglide, 5th-Airborne pin-box, Multi-vex mirrors, TST TPMS.
You should be getting way better mileage than that,when was the last time you cleaned the air filter or changed the fuel filter?
07 Z71 1500 4x4 6.0
08 3500 Dually 4x4 just for work
05 2500 D MAX 4x4 8 inch lift 37 inch toyos tuned,4inch exhaust,intake and more.
26ft Carson Inbox loaded for the toys
28ft Caliber One Boat
18ft Carson Car trailer
Which engine do you have? They changed in mid year in 2004. The early '04s had the LB7 which was known for injector problems. The latter '04s had the LLY which did not have injector problems. Look at your VIN, if the 8th digit is a 1 you have the LB7, if it's a 2 you have the LLY.
Either way, you should be getting much better mileage. I get 12.5 mpg hauling my truck camper, the truck and camper weigh in at 13,000 pounds. Empty and unloaded I can get 17 mpg.
I have a 2005 4x4 with 285's and I see an average of 14.5-16.0 average in town and the highest I have ever got is 23.5. The 23.5 was traveling at 55 mph in 60 degree temps and was hand calculated. On the average tank with mixed town and highway I can count on getting 16.
I would start with changing out the Air and Fuel Filters plus I would dump some good treatment into the fuel tank on the next fill up.
Stupid question but is there any chance that you might have a brake caliber that is hanging up? That can and will kill your mileage.
* This post was
edited 05/05/12 08:14am by TugCE *
I am a Retired U.S. Merchant Marine Chief Engineer
05 Chevy 2500 4x4 D/A with Helper Springs and Air Ride Air Bags
06 R-Vision RW3360 Fifth Wheel Toy Hauler
97 FLTCI converted into a Roadsmith Trike by The Trike Shop of Daytona