better to drive in 4x4

i am wondering if it is better to drive in 4x4 or 2wd to save gas. i know a AWD car gets better mileage because the power is put out at all 4 wheels so it takes less power to move the car. so i am wondering if the same is true for a 4x4. is it better to drive a 4x4 in 2wd or 4wd. im going to be doing a mpg comparisons to see whats better. but i would like some opinions on what everyone else thinks or knows. thanks

No the engine has to work harder to spin 4 wheels then it does 2 which in turn requires more gas. 4X4 is only for certain conditions other wise what would be the point of ever having your car in 2wd

And
If you use a it in 4W on dry payment you may burn up transfer case or a rear end.
Never run in 4W on dry payment.