window opened

[goots]

Is it alright to have a window opened by the sofa area when traveling down the road or dose your mileage drop??

[Harvard]

The open window may cause the water traps in the sinks and shower to burp foul odours.

[1492]

I think that since your motorhome was never designed to be especially aerodynamically streamlined, and is creating significant amount of drag already, an open window is not going to make any type of noticeable difference in mpg.