I tow an Escape 17B, dry weight 2100 lbs, actual weight loaded for a trip - 3010 lbs. I tow with a small SUV (a RAV4 V6 with tow package) rated at 3500/350 lbs. While the trailer weight is within limits, I have to load carefully to keep the tongue weight within specifications. Since the Casita 17's tend to have a heavier tongue weight, I'd suggest going to at least the 5000/500 rated vehicles.
By the way, over 45,000 miles of towing including the rockies & eastern mountains (yes, there are some), I've averaged 15MPG (25MPG unhooked). I rarely drive interstates, and usually tow at 57 - 60 MPH...