A 37' DP with a Cat 330HP should get 8+ MPG at 65. Slow down to 55 and you could get 10. You will not notice any difference in MPG towing a small car. We usually put as many miles on our toad as the MH so for us 7 + 45 mpg / 2 = 26 mpg overall on a trip out West now that I own a Prius.:B
In ten years of staying in mainly public CG I have not had any major problems finding sites big enough for my 42'. At 37' you can probably show up on Fridays without reservations and find a site big enough... I have to show up on Mondays when the locals have gone home.