I know this may seem unrelated but I am a substitute school bus driver.
A few weeks ago I drove a slightly Shorter than normal 2010 4500 Series Chev van chassis With a regular steel school bus body Bus. I'd estimate the weight right at about 11-12K lbs. (GVWR of 14,500lbs) This bus is a lot like a RV of that size and weight.
The digital dash readout said average 7.2 MPG and average speed of 16.0 MPH
Remarkable MPG for stop and go pickups, but it did seem correct. It had a 6.0L engine and was able to keep up with most any Car.
I can't imagine it would have problem towing a CRV around.