I paid £75 for the ScanGaugeE. It has a LOT of stuff it can do, but I am only really interested in one of its many features - the eco screen! Even if it won't ever work properly, one bit of info alone seems worth the price - the live feedback figure. Why? Well, my car has a live bar maxing at 60 mpg (the same a in our CRV). So, I have no idea how much better a certain speed or gear is at any efficiency above an indicated 60 mpg. From the 3 or 4 20 mile journeys I've used it on, there seems to be plenty of scope between travelling at 70 mpg or 110 mpg for instance. Yes, it does seem to mainly involve going slower (!), but I'm all about the MPG, not the MPH. I had enough of flooring it in my decade as a top pizza delivery executive!
I'm quite happy to chase this figure, and the average it displays beneath it.
I expect the average is meant to be a long term average, but due to my current problem with it, the average is of just each trip the car takes.
Also on this same screen is a bar scrolling left. It makes sense for you to have a look at the ScanGauge E site than I try and describe it probably.
(also, I sliced the tip of my finger earlier, so am typing with a little difficulty!)