for the most fat burning dont eat before workout and do your lifting first followed by treadmill for at least 30 minutes, longer if your up to it.
the reasoning behind this is to deplete blood glucose levels during lifting and force your body to access stored fat.
stored fat is always the energy source of last resort, survival mechanism, so dont give yourself easy energy and let your body break down those fatty acid chains for fuel.
you dont mention being a diabetic but i have caught enough **** from others about forcing down blood glucose that if you have diabetic issues just disregard this post