OK, maybe I'm not up to resistance level 5 yet. It appears to add about 30% to the resistance; before I used to burn 100Kcals in 10 minutes, this time I did 130Kcals. But it was too much hard work, so after 10 minutes I dropped back to level 4, and then only managed to do 15 minutes. total. Total energy expended is only around 20Kcals (or 2 minutes) less than normal, but I only made 2.3 miles.
2.3 miles, 15:01 minutes (so 9.2mph), 183 Kcals