I have tried to log every fill up for my 'new' VX for as accurate a picture of my actual mpg as possible as skipping tanks compromises the accuracy since the VX gas tank doesn't always fill up properly. I'm pretty sure I haven't skipped any tanks. You can view my gaslog if you like. Even though I only got the car a month ago, I have put over 10,000 miles on it. (yikes!) Lifetime mileage for the car since i've owned it is approximately 49.5mpg.
EDIT: I see now that it tells me the lifetime average under my alias. How come it doesn't show the graph on my new gaslog?