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The amount of zinc and phosphorus in motor oil was reduced even further with the latest API "SN" standard. Is there still enough zinc and phosphorus to protect engines from excessive wear? How about older engines, newly rebuilt engines, or engines with flat tappets? Should car enthusiasts look for ancient bottles of motor oil at estate sales? MotorWeek's master technician Pat Goss provides the answers in this four minute video: http://www.youtube.com/user/RockAuto.../6/xILCJc2o_L8