On my last trip up north to work, ( a 900 mile drive), I got a hand calculated 15.8 to 16mpg. The overhead deal was telling me I was getting 19+. Why does this thing read so far off? Is everyones' like this? I've noticed my mpgs getting better now that the winter diesel is going away for the season. So at least thats going for me.
Also, i figure I'm due for a valve adjustment, I'm at 164,000. Will this help mileage? And how do I do this? Can it be done at home with basic tools and a manual?

 

mine is 2mpg higher than hand calculated

 

I have stock sized tires and overhead is accurate. I thought mileage had gone up when I changed VP. Unfortunately, overhead was set to kilometers.

 

I reset mine just recently using the method in the manual & it is giving a much more accurate reading now....not sure if this helps but you might try doing a reset on it....

 

It can be reset? I must try it. My temp is off too..

 

this is a good website here if you needed to know what you need to have to do a valve adjustment.....i used this method last time i did mine & it works well.....

http://mopar.mopar1973man.com/cummin.../valve-adj.htm

 

yeah, it can be reset....check it out in the original manual & it will show you how to do it......

 

when I started adding alot of go-fast parts and electronics. I have reset my speedo according to my gps. but going down the freeway on cruise control and using the fuel economy settings. it show 32 mpg.. and I can honestly say its not true... I have gotten used to hand calculating... hell I'm still breaking in the rebuilt engine. less than 10k miles its not going to be awhile before the rings seat

 

www.fuelly.com

I use it and on my smartphone I punch the info in as I fuel up and it keeps track for me, pretty cool....

Im fr0gstrangler

 

I checked my manual and it only has how to reset (recalibrate) the heading indicator. Says nothing about how to reset the mileage part of it.

 

I know you can push in both buttons and it resets the milage.. is that what everyone is talking about .. have it displayed on your mileage and then push in both buttons same time????

 

oh, that just 'zero' it and starts it over, done that alot of times.

 

Yes, mine lies like a rug! Always shows 3 or 4 MPG more then what I hand calc'd. I reset the average after every fill up too.

 

mine is pretty good. within a few 10ths and i check every tank. a programmer or box will make it read way high.

 

My truck is bone stock and it read high,