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I have an 05 CC 2wd Duramax/Allison. This is my fourth Duramax. By far the 03 got the best fuel mileage and ran just about as good as the LLY. I hae driven several LLYs and all run better than mine, local diesel tech says it happens and no real reason why. Running at cruise control 70 It will get a best of 14.7 and a headwind will knock it down below 14. I dragrace and tow a 42ft enclosed gooseneck hauler(14,000#). Normal mileage is 8.9 towing 67 mph.. Headwind will take it below 8.0 I check all fuel mileage by filling to the neck and useing the trip odo. The truck indicator is usually within .1 to .2 mpg of the actual. This truck has 20,000 miles on it and the fuel mileage has not improved with age as I have towed with it from 500 miles on. The LLY has been a bit of a disappointment. I have owned Chevy trucks all my life and am not about to change but this particular truck is not the best one I have ever owned. My LB7 trucks would get 10 towing the same trailer and have been as high as 11.5 on no wind level ground.
Gary
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Hey guys, this is my first post, my first diesel pickup, and so greetings to all.
My truck is a 2005 2500HD w/ Duramax bought 6/1. The first 1,000 miles, the DIC said I got 17.4 overall. When it turned over 1,000, I reset it. Since then, overall, it's been 19.1.
Good points on slowing down above. That Allison tranny won't let me coast. I can see that driving habit changes will help.
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Purchased a 2005 Chevy 2500 HD Crewcab Duramax/Allison 2wd on 6/18. Just about ready to fill up my 1st tank and have been getting between 16 and 17 mpg according to the DIC with mostly city driving. I'll manually check that upon filling up to see how close the DIC is. I've been taking it easy, staying under 2500 rpm. Taking a trip this weekend and should be above the 500 mile mark listed in the owners manual, so I'm curious to see what kind of milage I'll get with all highway driving around 70 mph. This is my 1st diesel, which I bought for the towing capabilty. But, I will say it's getting within 1.5 mpg of my old 4.8l C1500 extra cab for the same daily work/home driving. Should exceed the gas burner while towing and not be as hairy to drive.
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1st tank of fuel last night. Figured my mileage (361 miles on 19.61 gallons), 18.4 mpg. All I can say is WOW. The DIC was off about 1.5 mpg, but who cares. That is the same mileage I was getting with my 4.8 gas burner in the same driving conditions. I'm interested to see if it get the same on a road trip. The gas burner would get around 23 (70+, air on, unloaded). I know the diesel will blow it out towing.
John
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Just bought a new Chevy 2005 2500HD LT Duramax/Allison yesteday. Had 3 miles on it when I left the dealer. I reset the DIC after driving home, about 25 miles, and checked it with the cruise control set at 60mph, it climbed to 18.5 after about 10 miles. How accurate is the DIC reading? Just curious, I intend to refill the tank and check it the old way this weekend. I test drove the Ford and Dodge and liked the Chevy best. This is a very nice truck. Also, I have noticed a lot of discussion about tire size. The dealer where I bought mine has 265/75s on his demo and said he thinks it lowers the power and fuel economy but shouldn't hurt anything or affect the warranty. I would really like to upgrade these 245s to 265s but don't want to lose much fuel economy, any opinions would be appreciated. (It doesn't seem like a 3.6% increase in diameter should have much effect)
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Checked the unloaded mileage the old way on my new 2005 Chevy D/A. In town, 100 miles 13.8 mpg. 200 mile highway trip Saturday, driving fairly easy 55-65 mph it got exactly 19 mpg. The DIC was fairly accurate also. It was saying 13.5 in town and 19.5 on the highway. I also upgraded to Cooper Discoverer ATR 265-75 E rated tires. I couldn't stand those little 245 tires . Speedometer is off a little, at 60 mph my GPS says 61.2 mph. Before changing the tires the GPS read 59 when the speedo read 60. I'm liking this truck more every time I drive it.
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I have a new 05' extended cab regular bed. with 300 miles on the truck I am getting 14.5 on the city, 21 on cruise control at 60 mph per the display
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I just got a new 2005 Dually Crew SLT 4x4, and so far the trip computer is scaring me, average is 10MPG....
Does the mileage really fall off on the 1 ton trucks?
My last truck was a 2500HD
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I just received my 2005 2500 hd 6600 and took it for a road trip kept it at 65 - 70 and if the computer is correct it was steady at 18.9 and on the ranch with hills and draws in 4 wheel it was at 17.8 I am pleased at this time.
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I have had a 2004.5 LLY 2500HD Duramax for a little over a year. I have a little bigger tires than stock and have heard wonderful stories about gas mileage. As a matter of fact, I have three different buddies with Duramax's 03' or later that have the LB7 engine and average 16-17 around town and have gotten 20 on the highway. I looked at my buddies lifetime average the other day and his was 16.5!!! His is about a year old, but he has the LB7. The guy at the dealership told me the LLY should actually get better than the LB7. What is the deal? My lifetime average reads 12.4 mpg and I have never gotten better than 15 mpg on the highway. I also have an Edge/Attitude performance chip.
I have also read all of these posts about 16-17 mpg and even 20 mpg or better. Most of my miles are unloaded with bed covered, and I do not have a lead foot. Could there be that much difference in engines? Any advice, help, or answers?