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Chevy Silverado and GMC Sierra Duramax Fuel Mileage

621 messages,  Last post on May 30, 2013 at 3:47 PM

You are in the Chevrolet Silverado & GMC Sierra Forum.

What is this discussion about? Chevrolet Silverado 2500HD, Chevrolet Silverado 3500, GMC Sierra 2500HD, GMC Sierra 3500, Diesel, Fuel Efficiency (MPG), Truck

Messages Page 2 of 63

#2 of 621 Re: DURAMAX FUEL MILEAGE [blackmax] by gagrice

Sep 19, 2004 (3:01 pm)

Replying to: blackmax (Sep 19, 2004 2:26 pm)
I got real excited about the DuraMAX when it came out. I read so many cases of mileage in the range you are talking about that I lost interest. I was hoping for 24 mpg on the highway and have not read of anyone getting that.

#3 of 621 by quadrunner501

Sep 19, 2004 (4:34 pm)

The worst tank I ever got was 17, and the best was 22. Overall average between 18-19, city and highway.
 
But...manual transmission (6 spd), and lightweight regular cab.
 
And the new LLY is a completely new design, new heads, new injectors, new garrett turbocharger.

#4 of 621 Re: [quadrunner501] by gagrice

Sep 19, 2004 (9:23 pm)

Replying to: quadrunner501 (Sep 19, 2004 4:34 pm)
And the new LLY is a completely new design, new heads, new injectors, new garrett turbocharger
 
Is that the new GM DuraMax? Is it a 2005 model engine? How is the power compared to the older models?

#5 of 621 Re: [gagrice] by quadrunner501

Sep 20, 2004 (7:21 pm)

Replying to: gagrice (Sep 19, 2004 9:23 pm)
The LLY was released in the 2nd 1/2 of 2004 year model run. It has more horsepower and torque, by exactly how much...I forget, something like 320 hp and 590 lb/ft torque, give or take a little.
 
The hp and torque increase is for Allison 5 speed automatic equipped models only, not the ZF-6spd manual.
 
The hp and torque of the previous LB7 was 300 hp, 520 lb/ft torque.

#6 of 621 The main features by quadrunner501

Sep 20, 2004 (7:44 pm)

...of the new Duramax LLY are the new heads, which put the injectors *outside* the valve covers, rather than underneath them as on the previous LB7. This is important because if an injector leaks, it will spill diesel fuel down the outside of the engine, rather than cause the crankcase to fill-up and overflow from the inside.
 
Unfortunately, that's exactly what's been happening. GM recently sent out notices to owners of 2001-2002 Duramax diesels that they *may* experience injector failure caused by high fuel return rates or cracked injector bodies, and that accordingly, GM will extend the warranty on *covered* failures (not all) to 7 yrs/200,000 miles. While that's a small positive step, my $0.02 is that GM has not gone far enough. Since they KNOW they have a problem with the Bosch injectors, the appropriate and ethical course of action would be to issue a recall for all affected vehicles, and replace the bad injectors with the updated ones the owners should have expected in the first place. FYI, these injectors operate under very high pressures, up to 30,000 psi, making them completely different animals than cheap injectors in gasoline engines which operate at a lowly 50 psi, and cost less than $100 each. The bosch diesel injectors cost upwards of $500 each, 8-12 hours labor to replace them, and some have been replaced 8 at a time under the GM warranty. You do the math...that's quite a bit of exposure for an owner to accept. Diesels are fun, but you could pay to play if you hold on to one beyond the warranty period. The bosch injectors are on national backorder at this time. Dealers cannot give a time frame if you are unfortunate enough to suffer this malady, except first come-first serve.
 
The other features behind the new heads and variable inlet garrett turbo-charger are primarily to address emission concerns and future low sulfur diesel fuels.

#7 of 621 Re: The main features [quadrunner501] by gagrice

Sep 20, 2004 (8:35 pm)

Replying to: quadrunner501 (Sep 20, 2004 7:44 pm)
That is good info. I was thinking of a used Duramax. Gives me reason to hesitate. Is there a problem if you do run the ULSD in the Duramax? You know I was so excited when they came out with that engine. I have held off buying a big truck to have it all sorted out. Now I don't know if I should go for the new Cummins or Powerstroke instead. I hate the looks of the Ford and Dodge.

#8 of 621 Re: [quadrunner501] by blackmax

Sep 21, 2004 (7:35 pm)

Replying to: quadrunner501 (Sep 19, 2004 4:34 pm)
I guees I will just have to ride it out and see what happens. I have friends who say they are getting 18-20 mpg. I have one friend that has the equipment to re-program the computer, says it gave him 2 more mpg. Any comments on this? First diesel for me, I'm green.

#9 of 621 by quadrunner501

Sep 21, 2004 (9:49 pm)

No reprogramming on mine...stock all the way. The quality of fuel can make a difference, also summer blends or #2 versus winter #1, which is thinner so as not to gel in the cold.
 
The cetane rating of fuel affects mileage and power, but it's hard get reliable information, or even know what you are getting at the pump. Find a reputable fuel source that you trust, and stick with it.
 
I think your mileage will get better, however if you have the newer LLY design, some reports are that it hasn't been getting as good a fuel mileage. It makes more horsepower, so the re-programming that matters most is possibly located underneath your right foot.

#10 of 621 2500HD Slow Acceleration by jwashin

Sep 24, 2004 (7:48 am)

2001 2500HD,6.0, Automatic transmission. Just bought used. When accelerating truck feels like its under load. Is this normal for this truck? How does yours feel. Also, seems like there is slight slip when going from a dead stop to start. You can feel it a little.

#11 of 621 Re: [quadrunner501] by blackmax

Sep 25, 2004 (4:54 am)

Replying to: quadrunner501 (Sep 21, 2004 9:49 pm)
Thanks for the info. How would I know if I have the LLY design? Is it on the new car window sticker or do I need to find an engine number??? Most of the Cetane I have found is 40, I hear there is a place around town that sells 44, I will check it out. Last tank got 15.8. Thanks for the info.

Messages Page 2 of 63

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