Mine does the same thing. In fact when I picked it up from the dlr on delivery, it was only reading 7/8 full. I of course whined about them not filling it up. Response of that's how they are new. OK? Anyway on it's first fill it went all the way to full. On second fill, 7/8 then 50 miles later it went full. I've been told it need a software update. Dlr is 100 miles away, so I'll try an update myself first. Regards, Bart