I always try to refill when I get to 50 miles left on the digital range estimator. I've gone as low as 30 before needing to refill. Has anyone run it down to 0 (and how far were you able to go afterwards)? During longer trips through more sparsely populated areas I find myself getting range anxiety so it would be nice to know what the LCs true range is. I drive a HE to the extent it makes a difference.