Exercise- Treadmill or Bike? =/?

I have both, and up to recently always went on the treadmill. I usually always did the same work out that pertains of first 25 minutes at the speed of 5.0, and the last 5 minutes just straight running at 6.0 and at the end I get a total of 2.55 miles ran and 355 calories lost, so today I said what the heck, let me go on the bike right afterwards and I did. I did 13 minutes on the bike and got a total of 2.6 miles and burnt 160 calories, I was also going at the speed rate of 12.5-13.00 mph should I just continue on the bike for 30 minutes everyday and only go on the mill every once in a while? thanks in advance.

Do both. It sounds like you have a great plan already. maybe do bike every other day and then treadmill the other days. Switching off will help with routine and help with the achieving the best results. When you only run and run constantly your body tends to get use to it and builds muscle memory. Making it slightly easy the more you do it. But that also means you would have to do a little more to achieve the same result. Switching off will max your result intake.

Bikes are also easier on your knees, legs and feet as it is a no-impact workout. Knees are a very sensitive thing, a human's knees weren't really built for a lot of running as it can slowly grind away the pad between your leg bones. You'll probably want this pad when you're older, so the less impact on your knees the better.

Bikes give you a better more thorough body workout. Treadmills are only good for cardio and leg tone.