What is the average mpg on a 2001 Jetta VR6?

i have a 2001 jetta gls or something, with a v6, and in the dash, it tells you the mpg, but the number jumps ALL AROUND, from 8 mpg, to 108 mpg, and sometimes "--- mpg," whatever that means.

i had a 2003 jaguar and it told the mpg, but it stayed constant and only changed when you drove erratically for a while.

i drove a 97 Chrysler sebring after the jaguar, and it got about 35 mpg, and my jetta seems to be doing just as well on gas however.