Thats too funny!
Bad Milage.....WOW
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Elder User
Joined: Jun 2003
Posts: 642
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From: Bay Area, CA
Bad Milage.....WOW
Well I expected better. Last year I drove the truck on a trip and averaged 14.5 or so. This time, I averaged 80 mph, (same as last time) and got around 11.6. The kicker was I added some diesel kleen to this tank, and I recently changed the fuel filter, and put in a brand new paper air filter before the trip. Is this the normal MPG for a 99 CC Dually with 373s? Did I experiance an unknown phenomenon on the last trip? It is ready for an oil change, but that wouldnt effect the MPGs though....would it? I slowed to 60, and the mpg went up to 17.0, but I couldnt imagine doing 60 mph for 747 miles 
O well, it was a fun trip, Im just looking for Ideas or opionions on this Thanks guys.
The trip was from Pheonix to San Francisco. -Dave
O well, it was a fun trip, Im just looking for Ideas or opionions on this Thanks guys.The trip was from Pheonix to San Francisco. -Dave
FTE Leadership Emeritus
Joined: May 2001
Posts: 13,653
Likes: 6
From: Cabot, Arkansas
My truck seems very sensative to the condition of the oil. If I run past 5K or so my milage will drop 1-2 MPG. Wind, weight, speed and terrain are enoumous variables to your fuel effiency. Change the oil, fold the mirors in and drive 55 and you'l get 20+..... 
like anybody is willing to do that for a few extra mpg.
like anybody is willing to do that for a few extra mpg.
Senior User
Joined: Mar 2005
Posts: 189
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From: Grantsville MD
I have a 2000 psd auto sc 4x4 and the milage is not good 11-12 mpg city, 15 mpg going 60 on the highway. It has got 285/75r-16 tires I don't know if that matters. I have been in several 6 spd psd, never mine is the only auto I have been in. When I am going down hill and apply the brakes my rpms drop 400-500, but then when I come off the brakes they go back up, is this normal? just got the truck 114,500 miles on it, it has an aftermarket intake, and a 4" exhuast w/ no cat. I thought these mods where going to help mpgs', if they did I would of hated to see them before. Any ideas ?
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Joined: Aug 2003
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Originally Posted by WMDPSD
I have a 2000 psd auto sc 4x4 When I am going down hill and apply the brakes my rpms drop 400-500, but then when I come off the brakes they go back up, is this normal?
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Senior User
Joined: Mar 2005
Posts: 189
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From: Grantsville MD
Originally Posted by whitmo
I have the same model truck as you do, and mine does the same thing. I think it is normal. I think it is the torque converter locking/unlocking. It is probably supposed to save fuel. My buddy's 03 Excursion w/ 7.3 PSD doesn't do it though.
well if it does the same thing then I guess it is normal. I thought maybe it was some sorta t/c lock-up mod, but i guess not. I think it is rather annoying. I would think that if it ran at the lower rpms all the time that would be better for the fuel savings than the higher rpms, just my 2 cents.
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FTE Leadership Emeritus
Joined: May 2001
Posts: 13,653
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From: Cabot, Arkansas
Originally Posted by Black88GT
Wow, a cat was just mentioned. I wouldnt loose MPG from removing a cat would I? I had one last year, and recently took it off 
Posting Guru
Joined: Aug 2004
Posts: 2,417
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From: Braham MN
Originally Posted by WMDPSD
well if it does the same thing then I guess it is normal. I thought maybe it was some sorta t/c lock-up mod, but i guess not. I think it is rather annoying. I would think that if it ran at the lower rpms all the time that would be better for the fuel savings than the higher rpms, just my 2 cents.
Some PCM codes, also know as box codes will keep the converter locke dwhen the brakes are applied until you are below 35 MPH others will unlock it when you touch the brakes, some will even unlock it when the gas pedal is returned to idle.THAT is ANNOYING!!!!
Check out this thread, totaly off subjuct but it might be worth you time.
https://www.ford-trucks.com/forums/s...d.php?t=317681
Diesel Rod
Hotshot
Joined: Dec 2003
Posts: 18,423
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From: iowa
a couple of things on the origanal question, My 2000 gets 14-15 in town gets consistantly 18-19 on the hwy at 65, and at 75 drop 15-16 and add a towed 15k lbs running 75mph I got 11.5mpg. now all this is in the summer with a fresh oil change when it''s getting time to change the oil all my MPGs drop by 1-2, and when I run blended diesel (winter blend around here is 50/50 with #1) my best fuel economy is 15. so what I am saying is if you needed to change your oil, and you put in blended fuel you will drop as much as 6mpg real easy, I don't know why but the PSD seems to be real sensitive to blended or types of fuel atleast both of the ones I have owned were.
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From: The Great Plains
Originally Posted by WALJON
what grade of oil do you use? I have a 96 and I use 10w 30 I get pretty good milage