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Two weeks ago, I purchased a used 04.5-05 LLY Duramax. 2500HD CrewCab 4x4 with 44k miles Do not have a manual with the truck.

Just had it serviced today. Does the oil need to be changed again at a 3k interval or a 5k interval?

I just finished reading all the posts in the DuramaxForum. I've seen the threads that speak of continous running fans, overheating, and low mpg for the LLY. I haven't noticed my fan running continously. I have noticed that the temp stays at 210 most of the time. It will drop with t-stat opening, but then it comes right back up and holds. This is my first "personal" diesel and I didn't expect it to run this temp. Should I be concerned? I bought this to tow my fifth wheel. Is there anything I should do? I was also expecting higher mpg. I haven't even towed yet. Not getting anywhere near what I expected. Truck came with a Supertuner Programmer. I'd rather keep it stock, but could the tuner help my MPG? Should I look at diff intake....like Volant or K & N ?

I wished I'd heared about this forum before I bought this truck and could've read these threads about the LLY.................:confused:

Worries of towing camper...losing power due to fan...overheating...and low mpg.......really got me :eek:
 

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Well, welcome to the forum! The oil needs to be changed about every 5000 depending on what type of oil you use. Actually you could easily get away with 7500....does your truck have a DIC (driver informantion center)? I would go with that reguardless of what oil you use. Some people just can't stand to let it go that long. As far as your engine temp....it is normal to run 210 when fully warm. Yes, the mileage could be a little better, but most people exaggerate their mileage claims. I found that out the hard way. If you aren't hand calculating your mileage, then you don't know truely what you are getting. A tuner could help a little on MPG within reason though...the biggest effect on MPG is your right foot. Pushing it from stoplight to stoplight won't get you any better mileage with a programmer. Keeping it below 2000 rpms cruising seems to help out. A intake will not help your mileage out and will introduce more dirt to the engine. If you do go with one, stay away from k&n....they are the worst with letting dirt through. If you don't hear your fan run constantly when you are towing, you got one of the good LLYs. You will know when it kicks on though. It will sound like a jet engine. All you can do is just drive the truck and not really focus on the MPG unless it is below 16 unloaded on the highway. That seems to be the norm....some get better some get worse.

Also, when you got your truck serviced, did they change the fuel filter? That is something you have to be religous changing with a diesel. I would not go too much past 10,000 miles on the stock filter set-up. If you want the manuals, PM me your e-mail and I can send you a copy of the one I have for my sierra.
 

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Discussion Starter · #3 · (Edited)
Thanks for the welcome!!

I am sticking with Rotella 15W40

Yes, my truck does have the driver information center..though I've been having to play with it and learn how to operate it on my own w/o a manual. I have a very light foot, do not take off from stops, etc. Generally truck has just been cruising at or slightly below 2000 rpm. I definitely haven't heard the "jet engine". I'm very satisfied w/how quiet my truck is. I will take the advice and hand calculate mileage to see what it is getting. I put a Volant CAI on my previous Dodge 3500 gas burner and it took mileage away. More air, more HP, ....more gas. Was unsure what effect one has on a Duramax. I think I'll just keep the tuner for code reading and not programming.

They did not change the fuel filter and didn't even mention it to me.

Every 10k miles religiously.......correct??? I'll ask previous owner if he had it changed. I doubt it, since he is not the "maintainance" minded person.

I've been trying to find a manual online for ordering. Any hints.....?? If not, I'll take you up on the offer...but will send you pmt for a copy and shipping. Long way from Alaska to Georgia!
 

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Hi, I'm Earth. Have we met?
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WElcome to the site!

I would keep the programer on, it will (should) help milage if kept on a lower setting like 60-80 hp. MY wife just bought a similar truck and it was only getting 14 mpg, after a little tuning its now running around 16. Also when using a tuner you DIC will be off on milage!
 

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I have it in electronic form. Although, you could go to mygmlink.com and download it from your glovebox there.
 
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