MPH in Diagnostic Mode
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Senior User
Joined: Dec 2004
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From: SW, Ohio
MPH in Diagnostic Mode
I had my truck in diagnostic mode today and I was watching the digital mph. I then compared it my analog odometer and there was a difference of about 1.7 mph. The analog was faster than the digital. Just wondering which one was more accurate? My guess would be the digital but I just wanted your guy's opinions.
Thanks
Thanks
Postmaster
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From: Lufkin
I would say the digital because it's run off the computer and all that good stuff. Plus, when you give your engine a real good rev, the tach doesn't even go up in time with the rev on th analog. I noticed the same thing on mine when I did it. It's actually pretty accurate with each other until you get to higher speeds, then the digital tach shows a slightly slower mph.
New User
Joined: Dec 2004
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Can anyone of guys give me some tips on running the MPH diagnostic on my 2000 F150?
I want to check the calibration of my speedo.
I have 3.55 gears and 285/75/16 tires and the speedo seems to be running slower than actual speed....1800rpm=55mph .
I want to check the calibration of my speedo.
I have 3.55 gears and 285/75/16 tires and the speedo seems to be running slower than actual speed....1800rpm=55mph .
Posting Guru
Joined: May 2004
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From: Indiana
Mike- I bet you're speedo in your dash is reading a little slow becuase you have 285's on your truck..those are pretty big. If I was you I would take it to the dealership and have it re-calibrated.
Laughing Gas
Joined: Aug 2004
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Originally Posted by horizonhuskies
Also keep in mind small variables like tire height, original gear ratio, etc.
Garrett
Garrett
I.E. they may be out of calibration, but they are out of calibration together? Or am I wrong? I am under the impression that the souce of tach/speedo is the same.
For instance, if you have 35" tires and throw on 4.56's, but don't get your speedo adjusted. So your analog speedo says 65, but you're really going 75. Wouldnt your digital speedo also say 65, even though wrong? Otherwise our digital speedo would always compensate for tire height and gearend, leaving our analog speedo in the dust.
Correct me if I am wrong, i like to where a thong, listen to my song, all mighty king kong
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New User
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I agree with you .
I just ran my truck with the 285's in the enG mode and the dianogstic read the exact same as the speedo.
I will have to get the wife out in her car and follow her to see just how far it is out before I go to the dealer.
I just bought this truck and was trying to get some kind of MPG on the first tank full.
I drove the truck so slow that my hair started turning blue-gray and only got 13.5 with a 5 speed.
I think it might be the 285's that are throwing things off.
I just ran my truck with the 285's in the enG mode and the dianogstic read the exact same as the speedo.
I will have to get the wife out in her car and follow her to see just how far it is out before I go to the dealer.
I just bought this truck and was trying to get some kind of MPG on the first tank full.
I drove the truck so slow that my hair started turning blue-gray and only got 13.5 with a 5 speed.
I think it might be the 285's that are throwing things off.
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Laughing Gas
Joined: Aug 2004
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I'm rolling 235's myself. 285-235 is 50 millimiters, which is rougly 2 inches thicker. That's quite a bit thicker, meaning quite a bit more traction/friction = lower mpg. That's probably a HUGE factor, 2 inches wider tire contact on all 4 tires.
On my 235's i get about 17-18mpg highway, and that's driving like a grandmother. I have no idea what gearend i have, I'm assuming its 3.55 but wouldnt be surprised if its 3.08. I too have a 5spd. When i drive like a kid, i get about 13-15mpg.
On my 235's i get about 17-18mpg highway, and that's driving like a grandmother. I have no idea what gearend i have, I'm assuming its 3.55 but wouldnt be surprised if its 3.08. I too have a 5spd. When i drive like a kid, i get about 13-15mpg.
Laughing Gas
Joined: Aug 2004
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Originally Posted by homer4.2
Manster- I'm sure you have 355's because if you have 3.08's you would get better gas mileage than that..
Maybe it does...and i'm just numb to the screams of mercy....
Postmaster
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From: Lufkin
Originally Posted by 4.2manster
That's what I would assume also... but (since i have no tach) 20-30mpg in 1st does not strain my engine very hard....
Maybe it does...and i'm just numb to the screams of mercy....
Maybe it does...and i'm just numb to the screams of mercy....
Heh, you get 20-30 MPG's in first?! MAN THAT'S INCREDIBLE!!! You should just stay in first gear all the time, your gas mileage would be great!
