Help...New to caravanning & towing

Can anybody help me? Myself & husband are new to caravanning as we have recently sold our motorhome and bought a Sterling Europa 470 and a 2006 Nissan Xtrail. Our Xtrail has a switch for 4WD, 2WD or Auto and my husband is wondering if it's a good idea when towing on country roads to drive with it in the Auto selection (we didn't have a Nissan Xtrail manual when we bought the vehicle).

Thanks in advance

Lisa