10k pace is too fast for a tempo in my opinion. A tempo run is designed to stimulate your lactate threshold with the result hopefully being able to run faster before lactic acid starts building which will make you slow eventually. i.e the rate of lactate production from the muscles exceeds the rate at which your body can clear it.
10mile race pace is more appropriate. and a continuous run of between 20 & 40 mins is a good workout. or just break it up a bit if your new to tempo's . like 2 x 15mins with 2 mins slow jog in between or even 5 x 6mins with 60 secs recovery.
As for the OP, just use two speeds, warm up and warm down pace being the same. so maybe 15mins@ 6.5mph, 25mins @ 8mph, 15mins @ 6.5mph. *modify speeds as appropriate to you.
Jeremy G what speed is your 8mile tempo at? Half mara pace or abit slower? MP?
Edited: 25/11/2012 at 12:14