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Just bought an 08 GMC Sierra Dually 4x4 SLT Duramax w/6spd auto tranny. Now my head is spinning with all this stuff im reading LOL. First off what type of motor do i have LLY, LBZ etc. I pull a 30ft toyhauler and i am wanting to improve mileage like everyone else. I have plenty of power for my need just want to improve mileage without doing anything too crazy or risk hurting anything. I am going to put the amsoil by-pass kit on after break-in. What about fuel additives? Do i need them? I live in Ohio so it can get a little cold in the winter. Do they help mileage? From what i understand, i can use any biodiesel fuel. I was also thinking about a programmer after break-in. Will this void my warranty and will they know if i have one installed if i have it serviced. I have more questions, but i wont kill everyone yet LOL. Thanks for any help i can get.
 

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I believe you would have the LMM engine. I also don't think a programmer will do a lot of good until you get some miles on it. I traded my LB7 and got a new 7.5 not long ago and the difference in mileage was significant. About 3 miles per gallon less with the LMM. Being a dually might have a little to do with it also but I think that just being new might be the kicker. Some companies, such as Diablosport, don't have the programmers available for the LMM yet anyway so you might as well just drive it a while. As far as additives, I am not a big fan of them because in my trucking days when I owned several highway trucks, the Caterpillar man told me to never put anything in the tank but clean diesel and I have never been sorry of that. I suppose if someone could show me the benefit or need I might change my mind but probably not. Just old and hard headed I guess.
 

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Addatives Will Help, Stanadyne, Amsoil Makes One, Lucas, Stay Away From Autopart Store Brands. Stanadyne And Amsoil Help Mileage, And This Ulsd Diesel Sucks So You Need It.
 

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Thanks railbird and Deesel man for the help, i found out today amsoil with the CJ-5 (DEO) series is not an extended life oil, so i am second guessing the by-pass kit since i will have to change the oil more often anyway. I need that oil because of the DPM filter, so they say. How about air intake kits or just changing to a K&N filter, are they worth the money?
 

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You might do some research on the K&N filters. I haven't noticed a lot of good being said about them on here. There is also some independent tests that have been done that show that the OEM filters are about as good as can be had. However, having said all that, there are some that swear by the AFE and some other brands.
 

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Congrats on the truck. You have the LMM engine. As for better mileage and mods and stuff. Don't waste your money on a Air intake...especially not K&N. PPE makes a programmer for your truck...but with towing...I wouldn't even attempt a programmer until you do an Exhaust mod, tranny upgrade, and get a Pyrometer and boost guage. Mileage will get better with time. As for fuel additives. I use Standyne. Some people say it's stupid...but I live in PA...so I use it. They say it stops fuel from gelling, cleans the injectors, and makes your gas more lubricitive. The way I look at it is, it's only like 75 cents extra a tank..and I do if for piece of mind...it won't hurt anyting. Just make sure the stuff you get, works with ULSD. And yes a programmer will void your warranty...but you can take the program out before you go for work....PPE does not leave tracks.
 

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Discussion Starter #7
thanks nouseforaname, do i need exhaust mod ,tranny upgrade, and pyrometer if i am going to run the programmer in tow safe mode? I am not going to run it to smoke the tires, just better mileage. I have friend that runs the bully dog in his ford on tow safe mode just for mileage and he doesnt have all those other upgrades. thanks for the info
 

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Well...from what I've read...and all the research I've done in the past 3 months...and I've talked to Allison tranny techs, and Suncoast...and I was told that if I ran a 40HP tune..with a Allison Jr shift kit..and didn't thromp on the pedal ever....that I would probably be ok. With the tow setting (90HP)...they said if I didn't tow anything..and got the shift kit...that it would be ok for awhile...but would eventually hurt it unless I upgrade it. There is a guy on here who runs a tune over 90, and he said he never has problems..but you never really know unless you try it. It all depends on where you live to...if you have alot of hills..you'll have more problems. And if you do get a tuner...you should def. at least do a Pyrometer...if you EGT's go too high....you are gona have big problems. You'll get different answers from everyone....so just make sure you know all the facts before you do it.
 

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you can run the PPE with the stock exhaust but things tend to get alot hotter and alot quicker that way so if you do a nice Cat back system it will really help out and then run the 90hp tune(witch is roughly 60rwhp since ppe rates at the crank)when runnin empty and if only loaded with less then 5k to 7k pounds you can run this setting but when you hit into the 10k or above i would drop it down to the 40hp level but you can(at your own risk)run the 160hp tune and i did for almost 40k miles and never had a lick of problems but i have a fully built tranny inmind in the near future so i'm not worried if the clutches are a bit burnt..as for the gauges,just think of them as a little extra insurance on a $40k truck.
 

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I also recommend the PPE programmer. I've been running PPE since the month I bought the truck.(05/05/04) Never had a problem except one day towing I went to clear out my egts and stomped for a little to long and blew the main. Still drove the truck and trailer loaded with a jeep commander home from North Carolina. Bullet proof tranny.... I do add additives to my fuel. Believe it or not MOTHBALLS. years ago there were studies showing that mothballs was like an octane boost. I have better fuel response and better milage. Every once and a while i put a qt. of synth. oil (what wt is to your discretion) to clean out the injectors and lube internally. Mothballs will if not used correctly will slow you down and clog injectors with sludge. DO THE RESEARCH FOR MOTHBALLS AND SEE FOR YOURSELF. (NAPTHALENE). GOOD LUCK
 
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