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You are in the Chevrolet Silverado & GMC Sierra
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Chevrolet Silverado 2500HD, Chevrolet Silverado 3500, GMC Sierra 2500HD, GMC Sierra 3500, Diesel, Fuel Efficiency (MPG), Truck
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
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]
Sep 25, 2004 (4:54 am)
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.
Sep 25, 2004 (11:55 am)
I don't know how you tell, unless it's in the VIN or engine code or something, or maybe on the certificate of origin or titling papers...
The old design is the LB7, new design is LLY, a mid-year 2004 introduction. The LLY has more horsepower and torque too, and apparently worse fuel mileage...but again, that could be a consequence of the driver.
Sep 25, 2004 (11:56 am)
Or, if you see something that looks like injectors on the outside of the valve cover, because the LB7 design has the injectors UNDERNEATH the valve covers, so you can see only the fuel rails.
#14 of 621 Re: [quadrunner501]
Oct 02, 2004 (6:48 pm)
Found an easy way to tell if you have the LB7 or the LLY that came out in mid 2004. The owners manual shows oil filler caps for each engine. The oil filler cap for the LB7 has the following: (Engine Oil, 15W-40W.) The oil filler cap for the LLY has the following: (Engine Oil, HUILE-MOTEUR.) When I raised the hood I saw that mine was the LLY. I understand that these engines do not get the fuel economy that the old style gets. Also, I ran a tank of fuel through with the tonneau cover rolled up and went from 15.8 to 16.8. I am now runing another tank through with the cover in place. I'll see if that really makes a difference.
#15 of 621 With tonneau cover in place..........
Oct 11, 2004 (3:06 pm)
blackMax, how about that fuel usage?
Oct 15, 2004 (10:54 am)
Fuel mileage dropped back to 16.0 with the cover on. BUT! I also found out that my tires only had 40psi in the front and 70 psi in the back. I have gauged them up to recommended 80psi and I am running another tank through. Will let you know.
#17 of 621 Re: [blackmax]
Oct 20, 2004 (1:32 pm)
2004 Crew short bed. I have been getting anywhere from 17-19.....current odometer: 2500 miles. Not too bad with a topper on the back. I'm guessing the mileage will get a little better once the miles start to season the engine.
Nov 21, 2004 (8:50 am)
Though I have now sworn off Duramax trucks, I have owned two of them, an '01 and an '03. I never got any better than about 15mpg average with either one. If you drive them no faster than 65 mph you can do better. I was making trips out west where 80+ mph highway cruising speed is the norm. There the D-max returned about 13-14mpg empty.
I have three Cummins powered Dodges, two '03s and now an '05. the '03s will cruise at 80--90 and knock down 20 mpg empty. They are also quieter and don't have an impending injector failure in their future.