Optimal treadmill incline, speed, and time for weight loss?

Hi - so I use the treadmill for weight loss. Now basic physics says that energy = force x velocity x time. So obviously higher inclines, more speed, and more time on the treadmill is better. But clearly you can max all of them, because you get tired -- if you do lower incline or lower speed, you can last longer. Or for a given time, you can go faster at lower incline or slower at higher incline.

I'm going to start targeting 30 minute treadmill workouts - now, should I do a heavy incline and practically walk it at 4mph or should I go nearly flat and run at 5+mph? How will my results differ in each of these scenarios? Thanks for the advice!

nobody knows?

I don't think there is an ideal way to do it.  I try to mix mine up when I can.  I'm stuck walking right now on the treadmill because of a shoulder problem.  Before that I would start out somewhat slow to warm up, then I would increase the incline to see how fast I could go at different inclines, then walk (not too slow) a bit to recover, and then push the speed to see how long I could keep up at faster speeds. 

Basically this is interval training and helps me to get through the workout by giving yself lots of little goals without getting bored.  Something like "Hmm, let's see if I can jog at 5.5 for 2 minutes.  Oh that wasn't bad, <walk a bit> okay lets see if I can do 6.0 for 1minute 4 secs. "

As long as you get your heart rate up and break a sweat I think you should do it however you like, and don't let it get boring.