real world fuel mileage

An RV wouldn't get good gas mileage on the way down if it fell out of a tree. However, when you compare it to driving a car and staying in Hotels where you live out of a suitcase, have to wear shoes all the time to keep your feet from sticking to the carpet and where last night's top sheet becomes tonight's bottom sheet with a clean top sheet added, I'll stick with the RV. And don't forget adding all your meals in restaurants. I know, because I traveled for the company before I retired.
If you must do the math and you don't like the answer, stop doing the math.