If your hunting a bad area ,example old brick road below about 6 inches down road covered with fly ash and pea gravel and dirt and grass,if you put in auto power say 8 the machine is still going to try and push machine to 16 power because of the factory setting it seems in these situatuion it is better to go manaul and ajust to area all the way up to 16.If in maual power it is going to stay at setting you set,auto it is till going to try and climb up to 16,manual seems to cause less feed back.Just what i learned from using it.So if someone drops item at your house in grass use manual up to 16 to try and locate it using auto might over shoot it.Dont know if iexplained it right.