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Old 04-24-2008, 09:21 AM   eBay Motors  #1 (permalink)
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Fuel Economy

I have a '02 Duramax and after reading many posts, seems I am getting GREAT mileage, cruise set at 65mph I get about 25mpg, around town about 18.7mpg, and with 11K behind me about 13.5mph. THis of course all goes out the window if I need to make up time..............
Problem is, I WANT BETTER. It's stock, with a K&N air filter. 57k miles
Have had 2 performance guys tell me to not chip it or do any mods( I guess they made split head injectors on the LB7 engine that do not like the higher pressures? which may be why the extended the injection system warranty to 250K). I have had 1 guy tell be to open up the exhaust.

Any input would be appreciated. Jimbo
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Old 04-24-2008, 12:04 PM   eBay Motors  #2 (permalink)
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Welcome to the forum! Are all those numbers hand calculated or going off the DIC? Did you buy you truck new or used? If you bought it used, someone could have left a tune in the truck and could be throwing off the DIC (if you have one, I don't remember when they added it to the trucks). Also, another thing to think of, do you fill up to the same spot in the tank all the time....fill slow and top off, or just go until the pump stops and that is it? Personally, if you are getting that great of mileage with the stock set-up, don't mess with it. Opening up the exhaust shouldn't hurt, but with the way fuel prices are, I would just leave it alone. Another question, what set-up do you have with your truck? (std cab, extended cab, crew cab, 2WD, 4WD, 6 speed manual or allison?)
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Old 04-24-2008, 01:41 PM   eBay Motors  #3 (permalink)
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I bought my truck new in 02. 2500 HD Crew Cab 4x4 shortbed, allison tranny, no DIC, my mileage record is all hand(or should I say calculator) figured. I always "top" off the tank, and usually pump slow to avoid the "foam". Not always the same fuel stations, but I only have had 1 tank that I got 8mpg, that was in Iowa.
Years ago I figured out that slow acceleration and slow stopping have big impacts in gas milage, brake, and tire wear.
About 70% of my driving is with my Tag-along Trailer behind, maybe the truck just likes not having 11K attached to it's backside.
We are planning a trip to Alaska again this summer, and since diesel has jumped 50% in price since last summer, I want to see if any options are out there.
Yes, that LB7 engine beats the new ones in economy, and the new price scare the &$^% out of me!
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Old 04-24-2008, 06:08 PM   eBay Motors  #4 (permalink)
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I don't think you will find any tuner that will give you any better fuel mileage than that! The exhaust would help with EGT's when towing but as for the rest of it, JMO, but I think you would be kicking a gift horse in the mouth! I just don't believe you are going to do any better than you are!
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Old 04-24-2008, 07:03 PM   eBay Motors  #5 (permalink)
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you may want to hand calc. those mileage numbers. The dic is alomost ALWAYS incorrect (mine said 20 city) hand calc. was 17. I get 11 hand calc. towing 10K trailer. Hand calc....as far as a tuner. I get better mileage and power gains with the tuner, not to mention the ability to change settings on the fly is great. The motor is strong so do not worry about adding a tuner. I think the tech slept throught the "tech class" a little too much. I would find another tech.
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Old 04-24-2008, 07:06 PM   eBay Motors  #6 (permalink)
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Quote:
Originally Posted by mrjimboalaska View Post
I have a '02 Duramax and after reading many posts, seems I am getting GREAT mileage, cruise set at 65mph I get about 25mpg, around town about 18.7mpg, and with 11K behind me about 13.5mph. THis of course all goes out the window if I need to make up time..............
Problem is, I WANT BETTER. It's stock, with a K&N air filter. 57k miles
Have had 2 performance guys tell me to not chip it or do any mods( I guess they made split head injectors on the LB7 engine that do not like the higher pressures? which may be why the extended the injection system warranty to 250K). I have had 1 guy tell be to open up the exhaust.

Any input would be appreciated. Jimbo

FYI the injector "special warranty policy" is 7 years or 200K from date of service. The warranty is because of the poor oem fuel filtration (14 microns at first) then GM realized the prob and installed 10 micron filters. Due to this.. I added a pre-oem 2 micron fuel filter to play it safe. Diesel fuel is a dirty fuel and sometimes one bad batch can clog the oem filter and cause problems. Always carry an extra just in case. I do.
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Old 04-24-2008, 07:09 PM   eBay Motors  #7 (permalink)
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milage

I have an 02 Ext. cab 4X4. I am also getting great milage when i learn to keep my foot out of it. i get 23 with the cruise set @65 and around town about 19. Again that is when i keep my foot out of it.
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Old 04-24-2008, 08:54 PM   eBay Motors  #8 (permalink)
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Sure like to have your truck for the mileage. Wana trade. Best I get is 15 driving 55-60 and 9.5 mpg towing 9k
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Old 04-24-2008, 09:00 PM   eBay Motors  #9 (permalink)
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Get'n 13mpg in town and 20-22mpg on freeway doing 65-70mph. Towing my 7500k wakeboard boat I am getting about 14mpg @ 60mph....
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Old 04-25-2008, 09:08 PM   eBay Motors  #10 (permalink)
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Quote:
Originally Posted by mrjimboalaska View Post
I have a '02 Duramax and after reading many posts, seems I am getting GREAT mileage, cruise set at 65mph I get about 25mpg, around town about 18.7mpg, and with 11K behind me about 13.5mph. THis of course all goes out the window if I need to make up time..............
Problem is, I WANT BETTER. It's stock, with a K&N air filter. 57k miles
Have had 2 performance guys tell me to not chip it or do any mods( I guess they made split head injectors on the LB7 engine that do not like the higher pressures? which may be why the extended the injection system warranty to 250K). I have had 1 guy tell be to open up the exhaust.

Any input would be appreciated. Jimbo

So you're saying that you get between 600 ( around town ) and 850 ( cruising ) miles per ( 34 gallon ) tank ?
Not to be a jerk but I find it really hard to believe my friend ...
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