ultra gauge and mileage questions

Ok I've had this for a while but was Curtis. Does anyone know why the start up protocol is j1850. The manual says that gm and Chrysler, just curious if it matters.

Also i hear guys talk of how they made the mpgs more accurate at each fill up. I can't quiet figure out how. When i hand calculate my miles or it seems i get 1 or 2 better than the gauge says. I've also noticed that for every mile i rebel my counts it as .9 or so. I have larger yours so i figured that would new the cause but I've heard that it is the gears not yours that cause this.

Can anyone explain this better for me.

 

Calibration can be tricky.
For one thing, though the UG's odometer and the truck's odometer get their data from the same source, they may not match.

Match the UG to a GPS and it will give you actual distance (stock odometer is a hair higher than actual on 2nd gen... not sure how 1st gen is calibrated)
Of course, tires impact this as well.

But in a nutshell, if you want the UG to be reasonably close to what you calculate, you first need to calibrate the UG's distance to match the truck.
Use the trip meter, reset the UG's distance, and reset it.
The more miles you go, the more accurate it will be.

Now the same for fuel consumption.
The more fuel you use, the more accurate the calculation will be.
10 fill-ups will give you a VERY good reading, but.....

Seasonal differences in fuel will impact fuel economy, as well as the UG's accuracy.
If you get a tank that has no ethanol, it will be off by a fair amount.
Normal driving, my UG is generally close, but it's never exact. UG might show 24.3 and I might calculate 24.5 or something like that. It's never been off by more than 1/2mpg.

 

How do you calibrate it with the diferrent fill ups? I tried it once and when I did it it jumped my mileage to like 40mpgs..do I have to keep track of how many gallon I put in it all ten times when I correct it?

Ive got a 500+ mile trip in a few week so ill recalibrate it while i do that.

 

Reset the fuel calibration at the same time you fill your tank.

Next tank, input that number.
Next tank, ADD the new tank numbers to the previous numbers... this will normally mean just a small adjustment unless the UG is way off.

I did the same as you and the whole time I was bringing it down I kept telling myself "There's something not right... it was displaying "28" for a reason...."

After a couple of tanks, you'll be closer, not right on, but "tolerable"
Now just ignore the thing for another 5-10 tanks... just keep a total of how much fuel you are putting in.
When you've loaded 100 gallons or so, go back in and correct it to match that number and you'll be reasonably close.

I'll be fine-tuning mine in a couple of days off of a 155 gallon base.

 

Ah ok that makes sense then lol thanks man i appreciate it.