National Geographic : 1944 Jan
Only Diamonds are Carbon Worth Keeping! Worth Keeping! Carbon is a treasure when it takes form in sparkling diamonds - but hard, black carbon is a destructive and waste ful thing in an automobile motor. If your motor is suffering from carbon (and many motors are) -start using Macmillan RING-FREE Motor Oil. It removes carbon while you drive! With RING-FREE you get a cleaner, more thoroughly lubricated, sweeter running motor. That results in better gasoline mileage. Have your crankcase drained and re filled with Macmillan RING-FREE Motor Oil today! Keep on using RING-FREE to save gasoline, to lengthen motor life and to constantly combat the destructive effects of carbon. MACMILLAN PETROLEUM CORP. 50 West50th Street, New York 20* 624 S.Michigan Avenue,Chicage 5 * 530 W.6th Street, Los Angeles 14 Copyright 1943 Macmillan Petroleum Corp. , LI By INDEPENDENT DEALERS EVER I E El'