What should the MPG be on a Duramax?

[chromebumpers]

Back in the fall of 2005 i ordered the highest performance diesel truck, an LBZ - approx. 20 hp and 25 ft lb torque more than the standard diesel. At that time diesel was the cheapest fuel and I was told diesels have great fuel economy over gas. the very week the truck was delivered diesel climbed higher than premium gas and has since stayed the highest costing fuel. This was my first diesel and it was a big mistake because I don't haul heavy loads or long road trips. I have 54,000 miles on it and the only mod is a Gale Banks Monster exhaust. My problem is my gas milage is 15.5 mpg (always) my last truck was a 6.2 Chevy gas with the very same crew cab and it had 17.5 mpg. Other Duramax owners say they get 22 mph average. what could be causing lower milage? I run clean filters, the top of the line Michelin tires with the recomended pressure, what mechanically can i check or do to increase the fuel economy?

 

[mathd]

get a better axle ratio if not already, get it tuned for economy(efilive?), use narrow tire, bed cover, EGR block/delete mod(this one said to help mpg alot).
Avoid using it as grocery getter.

 

[87vette81big]

I would trade off your Duramax Diesel Rich.
Buy a used Chevrolet Silverado 1500 4X4 with a 5.3 L V8.
Or buy a Ford F-150.

Diesels only great if your towing 4,000-20,000 pounds weight constant
Your only daily driving & light off roading.

Install 10 ply 4X4 tires. 16-17 inch rims.
30-33 inch tall tires.
Heavy Duty Nitrogen gas charged shocks. Off road style shocks. Rancho or similar.
Add a steering stabilizer shock.
Positraction rear diff handy for getting out of slick mud.

Roads in Illinois less than desirable also here.
Repaved maybe only Half since 2007.
Drive my K1500 4X4 Suburban daily now.
Can take the crappt roads

 

[chromebumpers]

get a better axle ratio if not already, get it tuned for economy(efilive?), use narrow tire, bed cover, EGR block/delete mod(this one said to help mpg alot).
Avoid using it as grocery getter.

The Allison does have overdrive, wouldn't a lower gear (now has a 3:73) just matter for highway driving? besides, wouldn't that be expensive because i would have to change both front and rear together? I'm not sure that's a job I can do by myself. I like a quite ride so I went with a strickly highway tread Michelin - I might add they have 20K on them and still look like new. I up one size on the tire change - going from a 245 to a 265 to allow flatter cornering. I do have a bed cover. Can you tell me more about the EGR Block/delete mod?

 

[chromebumpers]

I would trade off your Duramax Diesel Rich.
Buy a used Chevrolet Silverado 1500 4X4 with a 5.3 L V8.
Or buy a Ford F-150.

Diesels only great if your towing 4,000-20,000 pounds weight constant
Your only daily driving & light off roading.

Install 10 ply 4X4 tires. 16-17 inch rims.
30-33 inch tall tires.
Heavy Duty Nitrogen gas charged shocks. Off road style shocks. Rancho or similar.
Add a steering stabilizer shock.
Positraction rear diff handy for getting out of slick mud.

Roads in Illinois less than desirable also here.
Repaved maybe only Half since 2007.
Drive my K1500 4X4 Suburban daily now.
Can take the crappt roads

Brian, I have a 5.3 in my 2004 van and it has all the power I ever needed.

I don't get the 4X4 30 - 33 inch tires, they would be nosier on the road and use more fuel. So, switching to gas charged off road shocks will calm down the rodeo ride of the OEM shocks? Btw, my Silverado is a 4X4.

I was waiting for a totally redesigned GM truck so that i can feel current in style for a least a few years afterwards.

one last comment, anymore it seems there is not that much of a spread between a good deal new truck and a few years old truck. I always buy in late spring/summer when there is an employee pricing and the bigest rebates (if you're not taking the zero % financing). Do that and you see only 1 or 2 thousand difference between a brand new and something 4 years old that some body
may have leased and never changed the oil.

 

[mathd]

get a better axle ratio if not already, get it tuned for economy(efilive?), use narrow tire, bed cover, EGR block/delete mod(this one said to help mpg alot).
Avoid using it as grocery getter.

The Allison does have overdrive, wouldn't a lower gear (now has a 3:73) just matter for highway driving? besides, wouldn't that be expensive because i would have to change both front and rear together? I'm not sure that's a job I can do by myself. I like a quite ride so I went with a strickly highway tread Michelin - I might add they have 20K on them and still look like new. I up one size on the tire change - going from a 245 to a 265 to allow flatter cornering. I do have a bed cover. Can you tell me more about the EGR Block/delete mod?

Yeah i forgot all duramax come with 3.73, wich is good you dont want numerically lower for a truck.
said this because some older 6.5 with 4.10 ratio killed the mph on highway, and 3.73 helped them for 2-3 mph.
wider tire lower mph, try to keep them well inflated, stock size will help mpg.
EGRDelete/block, the best option is a EGR disable done wiht programming, EGR delete is alot of work, EGR block, the EGR motor end up blowing wich throw a code and you have to add fingerstick to eliminate the code. EGR disable is best, also i read US vehicule onthe road need EGR to be on the legal side.
EGR delete vs egr block vs egr disable.
http://www.kennedydiesel.com/docs/Duram ... Delete.pdf

Also, kennedy diesel
http://www.kennedydiesel.com/
and health diesel
http://heathdiesel.com/
Are good places for tunes, upgraded parts and stuff like that.
This forum(Dieselplace.com)
http://www.dieselplace.com/

Will be able to help you alot more then i can(they are really willing to help, just make sure to search the forum before asking questions because duramax mpg has been discussed alot on this forum so the answer may already be there).
Am alot more into the old 6.5 turbo, can't really help with duramax.

 

[chromebumpers]

Thanks Mathieu!