Yup, someone else pointed this out, it's actually 4,296 km.
"Apparently the AVE fuel usage uses a 32bit unsigned integer to keep the distance in millimeters. Once that overflows it will show 99,9L/100km.
2^32 = 4,294,967,296mm = 4296km. "
[edit] Just to get max nerd points, this is the same...