If an 85KWH range is typically 235 miles then: 60 235/85*60 = 165 miles 70 235/85*70 = 193 miles 90 235/85*90 = 248 miles From the 90% thread http://www.teslamotorsclub.com/showthread.php/50171-What-s-your-90 most 70KWH owners are reporting iro 210 miles Thats barely 25 miles less than an 85KWH and some extremes are almost at parity. Or alternatively, the 85 should be a 20% improvement over a 70. So if the 70 is 210 miles then the 85 should be 255 miles. However you look at it, seems to make the 70D excellent value. Another possibilty is that the drivetrain operates considerably more efficiently at the lower pack voltage of the 70, though I would have expected the opposite as current for equivalent power is lower.