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Discussion Starter · #1 ·
I have a 05 6.0 and I can't figure out why every 10,000 miles I loose another 1 MPG. Have taken it to the shop and they keep telling me this is normal since they can't find any codes. Started out getting 15-17 and an now getting 11-12 at 66,000 miles (Hand calculated). I change fuel filters every 10,000 oil every 5,000 and air whenever it needs it. Anybody have any thoughts?
 

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Similar thing happens to my 07 with 13k on it. For me it's been Oil changes. After 4,500 miles on DINO the MPG's go down pretty bad. Things I've noticed to keep MPG's up:

Oil changes
Fuel filters
POWER SERVICE (grey bottle) treatments (heavily).

Sounds like you need to dump quite a bit of the grey bottle in on some Shell/quality Diesel. and Take it out for a nice hwy trip and get that thing hot, and romp on it. also Check other things: Wheel bearing drag/brake drag, Fan clutch, ATF fluids, Rear end fluids, Hubs not disengaging? etc. Go over the whole truck and don't forget... Tire pressure.


I'm not an expert by any means with EGR's, but that might be a factor. sticking, dirty etc. Have a EGR expert on here give you some tips.
 

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Similar thing happens to my 07 with 13k on it. For me it's been Oil changes. After 4,500 miles on DINO the MPG's go down pretty bad. Things I've noticed to keep MPG's up:

Oil changes
Fuel filters
POWER SERVICE (grey bottle) treatments (heavily).

Sounds like you need to dump quite a bit of the grey bottle in on some Shell/quality Diesel. and Take it out for a nice hwy trip and get that thing hot, and romp on it. also Check other things: Wheel bearing drag/brake drag, Fan clutch, ATF fluids, Rear end fluids, Hubs not disengaging? etc. Go over the whole truck and don't forget... Tire pressure.


I'm not an expert by any means with EGR's, but that might be a factor. sticking, dirty etc. Have a EGR expert on here give you some tips.
Ive pretty much found the same thing out, When I run powerservice I pick up a mile to the gallon, also when I run the "Red Fuel" I pick up 2 miles to the gallon on that alone, fuel quality has alot to do with it, I can get fuel at one station average 13.5 hand calculated can get it at another local station and get 16. Filters make a big difference to.
 

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I guess my truck is diff. than yours. I went to 6k for an oil change and my mpgs went up. I usually get 13.5 (before sct) and I was almost to 15 mpg when I had the oil changed. After the oil change I was back down to 13.5.
Just for input, fuel filter was changed 6k miles before with the last oil change.
 

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I have a 05 6.0 and I can't figure out why every 10,000 miles I loose another 1 MPG. Have taken it to the shop and they keep telling me this is normal since they can't find any codes. Started out getting 15-17 and an now getting 11-12 at 66,000 miles (Hand calculated). I change fuel filters every 10,000 oil every 5,000 and air whenever it needs it. Anybody have any thoughts?
Mine drops in between oil changes seems to go up when I change oil.:nod:
 

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Discussion Starter · #6 ·
Have tried different fueling stations but no luck. Would it help to take the converter off of this thing and let it breathe. I'm trying little things at first before I try to jump off the deep end. Has about 3,000 miles on oil and is really black so I'm going to change it today if I get time. Changed fuel filters at last oil change. Tranny fluid looks good (replaced about 15,000 miles ago). Air pressure is good in all tires. Is the egr hard to clean?
 

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No idea on EGR, haven't even seen mine yet. I'm sure I will some day. If the converter is plugged, yes it would help. but if everything is "good", then no technically. the stock exhaust system w/out muffler and w/out kitty is a pretty decent setup FYI. As for the oil changes and MPG's... one would think the longer you drive it the better the MPG's should get b/c the Visc of the oil thins, creating a thinner oil and less internal energy to move it and overcome the syrup. However, the other side of that same coin... the additives in the oil that help lower friction get worn out and the oil bogs down with Particles of carbon. So who knows. I like my 5-40 rotella.

One other thing... with that many miles have you thought about the MAF being dirty? b/c if you run a KN filter you get dirt on the hot wire and then it's not as crisp later on in life. and You also should look into the Intercooler & piping. Make sure it's not loaded with Oil. Probly wouldn't hurt to pull it and flush it or something. Look into that. and Your thermostat. If you're not running Warm... your MPG's will suffer. try changing the Thermostat with a OEM temp. I've seen Tstats break open and the vehicle always running cold and with bad MPG's. Happen to my personal vehicle.
 

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Discussion Starter · #8 ·
Pulled the egr and it was pretty nasty. Cleaned it up and it helped some. I'll try cleaning up the maf. Whats a good way to flush the intercooler. I noticed the carbon on the egr was a little moist. Is that a problem?
 

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To flush the IC, I had some Turbo Supras and what I did was Pull the IC off the car, and pour some Gas in it and swish it around. and then Flush it with the Garden hose VERY well and some compressed air, and let it dry out. Worked great everytime. the Gas thins out the Varnish and Oil in it, and then the Water removes the Vapor and chemicals from it. You can Hook a shop vac up to one end and suck dry it much faster FYI.

I have to find out where my EGR Even is....
 

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Discussion Starter · #10 ·
egr is to the left of the oil filter on top of the motor when facing from the front. Its held by 2 bolts and has a wiring harness that plugs into the top of it. Wonder whats the easiest way to pull that IC out without dismantaling the front end.
 

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I was reading on another thread about bad mileage too. my 05 has gotton 11-12 mpg since day one. it has a leveling kit with 35's.stock programing,a brute force intake and straight pipe.i cleaned the egr valve and didnt see a difference. change the fuel filters every 15k, change oil every 7.5k,and had the tranny flushed at 60k. im at 65k now and 11-12 mpg is what it gets.i dont let it run to warm up it gets plugged in.and on long trips over 400 miles never seen it over 15mpg. it runs perfectly. thats just what mileage it gets!
 

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My 2007 (build 2006) has TWO tranny filters, one in the pan, the other a cannister type. My mech told me a lot of techs change ONLY the tranny pan filter. He changed both and my mpg increased immediately, shifts were crisper. He told me the cannister filter will restrict the flow of oil if clogged, causing weak shifts and sluggishness. The paper filter was small, about the size of two adding machine printer rolls stacked.
Hope this helps.
 

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Discussion Starter · #13 ·
Finally got an opportunity to take it down the interstate and the egr cleaning helped. Now getting 15-16 on the dash (will figure stats manually after a tank or two. Still going to cut out the kitty cat and hopefully that will help some more. Will also check on the tranny filter thing. Thanks for the help everyone!
 

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I had both filters changed when they flushed the tranny. but honestly i didnt see a difference. it has been in to the dealer for the cold start reprogram . The one that makes the injecters run after it turned off. I just moved to northern oregon, so maybe flater ground will make it get better mileage.:dunno:
 

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My 2007 (build 2006) has TWO tranny filters, one in the pan, the other a cannister type. My mech told me a lot of techs change ONLY the tranny pan filter. He changed both and my mpg increased immediately, shifts were crisper. He told me the cannister filter will restrict the flow of oil if clogged, causing weak shifts and sluggishness. The paper filter was small, about the size of two adding machine printer rolls stacked.
Hope this helps.
How many transmission filters are on a 2004? I having the dealership flush my transmission fluid today, among other things and want to make sure they get both filters if there are two. Thanks in advance for the help.
 

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I was reading on another thread about bad mileage too. my 05 has gotton 11-12 mpg since day one. it has a leveling kit with 35's.stock programing,a brute force intake and straight pipe.i cleaned the egr valve and didnt see a difference. change the fuel filters every 15k, change oil every 7.5k,and had the tranny flushed at 60k. im at 65k now and 11-12 mpg is what it gets.i dont let it run to warm up it gets plugged in.and on long trips over 400 miles never seen it over 15mpg. it runs perfectly. thats just what mileage it gets!
How often do you touch your brakes? The goal should be to never touch them while driving. Ease up on the skinny pedal and see if that makes a difference.

No idea on EGR, haven't even seen mine yet. I'm sure I will some day. If the converter is plugged, yes it would help. but if everything is "good", then no technically. the stock exhaust system w/out muffler and w/out kitty is a pretty decent setup FYI. As for the oil changes and MPG's... one would think the longer you drive it the better the MPG's should get b/c the Visc of the oil thins, creating a thinner oil and less internal energy to move it and overcome the syrup. However, the other side of that same coin... the additives in the oil that help lower friction get worn out and the oil bogs down with Particles of carbon. So who knows. I like my 5-40 rotella.
I was going to comment on the viscosity, but you make a good point about the oil breaking down...

Finally got an opportunity to take it down the interstate and the egr cleaning helped. Now getting 15-16 on the dash (will figure stats manually after a tank or two. Still going to cut out the kitty cat and hopefully that will help some more. Will also check on the tranny filter thing. Thanks for the help everyone!
I don't think removing the cat does much besides "make it sound cooler"
 
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