Leave it in drive most of the time,use the tiptronic side of the gearbox for say large motorway hills.I find this better than letting the car decide what gear to use.The cruise with the van on is not much use really,again i find it makes the car keep hold of the high gears so i dont use mine, yours maybe better though.The gearbox is an Asin tf 80,fitted in a range of cars including mine,fitted with torque converter,now considered low spec due to being 6 speed and torque converter.But bomb proof,change the oil every 30k which is dead easy to do.Again the D5 is also bomb proof,a real nice bit of kit.