Should I trade in my SUV for a fuel efficeint car?

I currently own 2 SUVs that get 17/21 fro mileage. We have 3 1/2 years left on both loans. B/c of increasi- $1ng gas prices and the drop in SUV resale we owe more than its worth. I was thinking of getting a used honda or mazda 4 cyl. b/c there mileage is 24/35. If I trade in I will have to put up $4000 - $6000. This would drop my monthly payment by approx $100 - $150 per month. Not including the gas I would save. I drive 72 miles round trip to work. So, So I trade in or stick it out for 3 more years.