Hello everyone!
I was checking the forums for my mpg readout problem, but couldn't find any threads, so here it goes.
The mpg readout of my MCC 2010 has gone crazy twice in the past week. The readout goes from 99 to 26 to 16 to 32 to 27! It's all over the place. I'm worried about this . I made it stop by pressing the select button.
Any thoughts?

 

You mean the readout of the current MPG? Yeah, it changes moment to moment as you drive.
Depening if you're accelerating, going uphill, downhill, etc...etc... what your engine is doing at the moment.
It all evens out in your AVG MPG readout.

 

Thanks for your post.
I understand that it should vary while driving. It varies by .1 or .2, but the readout was jumping from 99.0 to 32.7 to 16.7 to 27.3, just to say a few numbers. Today I recorded the readout as it changed. I am going to see my MA tomorrow, I will definitely show him the video.

 

If you click through the menu and stop the instant reading, it will bounce all over the place. Going down hill off throttle, it will max out at 99mpg. Getting on the gas will take it way down into the 16.xx mpg range.

The other selection is average mpg and that is the average from day one.

Have played with all the selections on my wife's 2009 Clubman.

 

Have to agree with except ave read out is from when it was last reset, not from day one. Even then then average mpg can go all over the place in the first few miles after reset dependant upon driving conditions.

 

^Good point.

There are two distinct MPG readouts on the OBC:

1) Average
2) Instantaneous

It is normal for Instantaneous to bounce all over the place. If you are accelerating spiritedly, it may be ~10mpg, if you let off the throttle completely, it will be 99.9. It is merely showing your MPG at that INSTANT.

Regarding the Average MPG, typically, this doesn't vary as much. For instance, if it has never been reset since the car was new, it is the average over the entire life of the car, and therefore, you are going to see .1-.2 changes at a time usually, and you may go days/weeks without any change if the average is over a long enough period of time.

That said, like caveman mentioned, if you reset the *Average* mpg by holding down the OBC button while it is displayed, it WILL vary almost as if it is an instantaneous reading until it has a significant amount of time to average over.

Hopefully that made sense.

 

Thank you guys!
What can I say; I'm overprotective and worry too much!
I did what you said, and you are absolutely right.
Thanks for all your comments!