At 6 minutes a mile ( or faster) you should be able to destroy an old guy on a bike.
yesterday - 8 miles easy in 59:53 on loose dirt/sand up and down a 2 mile road, set out for 7:30s so I'm pretty happy about my judge of pace. Hot out there, real hot.
today - 6 mile jog no time, strides. Taking it easy for tomorrow. (if all goes right 10 miles hilly at MP)