I'm sure it's not a glitch, but why can't I get a true "current" mpg number when driving highway for an extended period of time? It fluctuates in huge increments rather than go up or down according to driving style. It will read 20, then 50, then 15, then 30. Doesn't seem to want to stay set at one number, or adjust more slowly and in tenths.
All cars are different w/this, but my car I will reset the mpg at fillup, and it will increment up until I have reached what it maxes out at for a true mpg. When I get into the city, it will adjust down slowly depending on how much city driving I do until it gets at it's true mpg. The Mazda's seems to do a "nations daily debt" scroll ( but not up as much) in terms of how much it adjusts.

 

There are two different displays for MPG. One is "current" MPG which is what your MPG is at that exact moment -- this can shows ranges and change frequently like you described above.

If you press info and scroll through the info view options, you'll see the average MPG which is the total average since the last reset..this should be a fairly level number without huge swings. To reset the average, hold the info button while it is displayed.

Hope that helps!

 

Yes I have gone off the average for a better idea of what it's getting city/hwy. But I won't know the highest mpg number on this thing until I do some serious long distance highway driving. I just find it odd how the numbers on "current" jump in tens and twentys rather than in ones and fives when it's calculating mpgs. Thanks!

 

The actual MPG I get in my new 2013 Mazda CX-9 is at least 3MPG less than what advertised, both for hwy and for city. And in cold temperatures it is significantly worse. I think Mazda tested the MPG going down mount Fuji with tail wind...