Actually, this appears to working correctly IMO. While I don't have my Edge yet, my Inifniti has this same feature and the numbers are extremely erratic depends on how I'm driving. If I'm stopped, the instant fuel economy will sky rocket, if I go WOT for a short amount of time, the instant fuel economy will skyrocket, etc. This is instant fuel economy, not average fuel economy, so you will definitely see large spikes.