Just purchased a new car that utilizes my iPhone as an onscreen Navigation system when plugged into the car's HDMI port. The system works great (even better then my F150's Sync system) but was wondering about how much data is actually used while on. I don't use the navigation that often and I don't worry about using data for normal car trips but how about long drives. If I'm on a long drive, lets say 8 hours between SF and LA, does this amount of time use a huge amount of data? I realize there's no reason for the map to be on for the entire time but I was just curious as to how much data is used for Apple maps.