excessive oil use in my Class C Freedom Express

You need to find out the height of your RV, but it is not likely that for a non-basement type C that the height is more than 12 feet.

Big trucks are usually sized to be OK at 13'6" which is the minimum clearance for the Interstate Highway system (or 14' in some states). Nobody should be building RVs that need more clearance, since operating them would require oversize vehicle permits.