Stroke

I run a tru speed to cal my speedo. Its dead on at 55 and 60.
My speedo is faster on the bottom and catches up by 55 mph.
Above 60 it starts to fall off (slower than actual).

You have to test at 3 speeds to get and average.
Test at like 20, 50 then 80. (easy to do with a GPS).
You still have to see if the trip and odo match to 1 mile with mile markers.
This also at 3 different speeds to get and average.

As far as the tach, remember its a ford gauge its more for looks.
It can be calibrated some. On the back of the cluster there is a trim for the calibration. You need to check the tach with a scanner. While trimming the tach it must be upright as installed in the dash.

Testing of average mpg should be atleast a 3 tank test.
The refuel should even come from the same pump.

23 mpg at 80 + is not possible. Its even tuff at 55 mph.

.02- Just sounds like 1 of those overhead MPG meters.
Bill

 

i could buy 23 mpg out of a tw on econo doing 55 mph, but not 85. i can get 19.8- 19.9 out of my rig doing 55 so with a tw chip in my truck on econo i should be over 20 with no prob's assuming i stay at 1500 rpm's when i jump up to those speeds my tach matches yours, 2500+ rpm's at those rpm's short trips on the highway drops me down to 15 mpg

oh, and according to gps, my speedo is dead on at 60 mph, once i hit 65 and up it is 2 mph off up to the stop at 90. below 60 it varies from dead on to 1 mph off