Accuracy of Gauges?

[92E34]

I was driving on the highway at 85 indicated and held on cruise. I hit the avg mph on the obc and hit reset. It was saying that i was doing 83.3 mph. Is there some sort of glitch somewhere?

Same deal with the tach. Its like there is a lag in time from when I change the throttle position.

[DaveVoorhis]

At least for the speedometer, that sounds about right. Mine is rather optimistic compared to the OBC average.