I have an '02 LB7 with 75k this I bought used in '04. I maintain it well. Truck has alway been great. I have a juice attitude on the truck that I installed about 4-5 years ago. I almost always keep the juice on 0 or 1. I tow a 12k fifth wheeler and bought the juice hoping to improve performance and gas mileage while towing.

A year or two ago, I noticed what I thought was a gradual loss of acceleration with a increase in injector noise. I occasionally have a little black smoke when I step on it hard. Never seen any other color smoke. Power is still OK, it's just that acceleration doesn't quite seem to be what it used to be. I paid an hours labor for the local chevy dealer to check the motor out in '08. They say everything is OK. However, they very seldom see a duramax.

My mileage was around 16-17 in '04, now it's more like 14-15 (slow decline over 6 years.) Seems to be about the same hwy/town. I get around 10MPG when towing the 12k trailer on flat ground (I live in FL). I don't really know if the towing mileage has changed as I can't seem to find my records while towing.

I don't see any fuel in the oil, and my radiator fluid hasn't changed.

Truck runs great, other than my perceived loss of power. I don't want to tear into the engine unless there is some reason.
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I had sent the above to dmaxaliTech as I was hoping to stop by his shop during a trip up north, but can't make it now - this was his reply.
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"Robert, its a good possibility that there is some slow degradation of the injectors. Pretty common for performance to suffer slowly overtime."

Thanks for your reply Eric

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My follow up question to any techs (Eric is so busy I didn't want to single him out again) is a slow degradation in performance/mileage any indication of impending injector failure or just something which happens? I don't mind at all putting up with the current mileage - it's not worth $3k to replace injectors just to improve mileage. It's just that we have just retired and are starting to use the truck for longer RV pulls. I would hate to be in the middle of nowhere and have injectors go. However, I don't want to tear into an engine that's seems to be OK. Sorry for the long message. I appreciate any suggestions. Robert.

You cleaning/changing the air filter and cleaning the MAF sensor? Fuel filter changed?

This may sound crazy, but when My mpg started to decline when I had to remove my ppe tuner, and couldn't afford to treat the fuel with stanadyne. So I bought some RedLine diesel fuel additive..slowly my mpg improved. Not what it was with the tune installed, but I'm getting about 3-4 more mpg than previously..Worth a try..?

You cleaning/changing the air filter and cleaning the MAF sensor? Fuel filter changed?

Yes thanks Ski, I am. I bought the shop manuals when I bought the truck. I maintain it well.

This may sound crazy, but when My mpg started to decline when I had to remove my ppe tuner, and couldn't afford to treat the fuel with stanadyne. So I bought some RedLine diesel fuel additive..slowly my mpg improved. Not what it was with the tune installed, but I'm getting about 3-4 more mpg than previously..Worth a try..?

I bought a couple of cases of an additive from Kennedy when I got the truck. So the additive hasn't changed. I'll probably use the last of it this year and will try redline. Thanks Hammer.

My mileage was down to 14-15. Changed oil 5w40 - transfer case and transmission to tran syn 295 - both axles syn. - air filter - new tires - back to stanadyne mix performance and lubricity. Mileage now in low 20's and runs like it is new. Fuel filter not due.
Did drain radiator and refill.

42,000 mile 03'
Blue Ridge Diesel in Va. sells stanadyne reasonable

What and where is a MAF sensor????????

My mileage was down to 14-15. Changed oil 5w40 - transfer case and transmission to tran syn 295 - both axles syn. - air filter - new tires - back to stanadyne mix performance and lubricity. Mileage now in low 20's and runs like it is new. Fuel filter not due.
Did drain radiator and refill.

42,000 mile 03'
Blue Ridge Diesel in Va. sells stanadyne reasonable

What and where is a MAF sensor????????

It's on the top of intake tube that goes from the air filter to the turbo closer to the air filter. It's square looking with wires connected to it. You may need a special torques bit to remove it. After it's remove get some MAF sensor cleaner and spray the small wire resistors to clean them.

It's on the top of intake tube that goes from the air filter to the turbo closer to the air filter. It's square looking with wires connected to it. You may need a special torques bit to remove it. After it's remove get some MAF sensor cleaner and spray the small wire resistors to clean them.

And don't lose a screw like I did!

My mileage was down to 14-15. Changed oil 5w40 - transfer case and transmission to tran syn 295 - both axles syn. - air filter - new tires - back to stanadyne mix performance and lubricity. Mileage now in low 20's and runs like it is new. Fuel filter not due.
Did drain radiator and refill.

42,000 mile 03'
Blue Ridge Diesel in Va. sells stanadyne reasonable

What and where is a MAF sensor????????

nice, i had 5-40 in my truck over winter aand this spring when i still had it in i was getting 16-17 driving like i always do and 17-18 (trying to:cool:) drive nice, changed oil and put 15-40 back in- now i get 16 babying it, 14 driving normal, lame