I just got a 2500hd LB7 about 3 months ago. It is chipped with a afe cold air intake. The last four weeks I have been getting only 10-13 mpg when I normally get 16 - 20 mpg. The only reason I assume its injectors is because of the louder then normal knock (sounds like a ford stroker) when it gets to temperature. I have cleaned the air filter, which get pretty bad after only 3000 miles or so. I am going to change the fuel filter, just havent had time. I dont have white smoke but I do have some loss in power. Any ideas?

one last thing, the injectors were replaced at 44,000 miles, right now im at 81,000. If the problem is injectors, its not covered under the warranty, because they would be the third set of injectors. So if it doesnt sound like an injector problem... Please, please let me know, might help me stop worrying about the $4000! Thanks

It does sound like a injector is popping, loose the chip for a while, take it to the dealer and tell them what you have and let htem chack the balance rates and stuff. I don't know what year truck yo have but if it is a 01-03 lb7 you have a 200k injector warranty. I have had to change filters within a few thousand mile because of some bad fuel I picked up. Change it before you ahve the dealer check the truck, loss of power could be from clogged fuel filter and air filter. I would look real close at the air filter. Make sure you can see sunlight thru it if you can. If not you will need to replace or if it is one that you have to oil, clean it real good and reapply oil on the gauze. most have a red tint so you will be able to tell if filter is covered ok.

No matter what year the injectors are covered until 100,000 miles/5 years. If you can, get the balance rates, but make sure you pull the chip before doing anything else.

Why don't you fill out a signature and put your truck into in it, including all mods made.

the the oil for fuel

I checked for any DTC's, but it didnt report any. I usually get a P0181 Fuel Senser but didnt this time. Its been cold so I keep it plugged in and I think thats why I get the code? I havent checked for fuel in the oil, will in the morning. I thing I did forget to mention - I was going to change the fuel filter but didnt have a big enough wrench on hand, so I drained the filter. What came out, from the look & smell of it, it was gasoline. How bad is this? could this have been in there since I bought it? I would have know if I had put gas in by mistake. Can that clog up a filter quick? I have also been using Lucas Injection Cleaner, recommended amount, good or bad idea? Anyway drove it for about twenty minutes, seemed to be fine, went up some good sized hills and temp came up a tick, but dropped with in 30 sec., When I pulled in it had the same loud knock at 850 RPM and got quite when I put it in Park at 750 RPM

I have a diesel fired coolant heater and it makes the truck throw code p0181 when it's too warm. With the Predator on 85 my power is WAY down until I clear the code.