I'm currently trying to increase my running speed and endurance. I currently have an 8 minute mile (on a good day.) My major goals are to achieve a 6 to 6.30 minute mile, 12-13 minute 2 mile, a 19-20 minute 3 mile, the ability to run 5-8 miles at a 8 mile per hour rate, and be able to run at a slow job pace for 15-20 miles straight.

I decided to start interval training to help increase my speed and endurance. This is usually my daily running routine.

warm up; 5 minute, slow pace jog at 5mph
Increase to 7.5mph for 1 minute
Decrease to 6.2mph for 2 minutes
Increase to 8.0mph for 1 minute
Decrease to 5.8mph for 1 minute

and repeat the process 4 times (minus the warm up) and conclude to workout with a 5 minute cool down; I do this every day of the week.

Also; I've been told that I should NOT be using a treadmill? Is that entirely truthful?

Looking forward to everyone's critiques and I'm looking forward to improving. Thank you all.