I have a 1952 Hudson straight 8 and this engine uses a splasher type oil system that requires only 4 lbs of pressure.  Does MMO reduce the anti-slinging ability in modern oils or has an ability to allow the oil to be misted for part coating that this type of engine requires? Also what are MMO’s properties to reduce flat tappet wear since modern oils are reducing the amount of zinc?

Marvel Mystery Oil has a viscosity of approximately a straight 5W oil.  At the 20 to 25 % replacement level, Marvel Mystery Oil will lower the viscosity grade of higher weigth oils.  For example, if you are using a 20W50 oil, the viscosity will be reduced to about a 10W40; a 10W30 or a 10W40 oil will be reduce to a 5W20 or a 5W30.  Using it in a 5W20 or a 0W20 will not affect the viscosity of the oil.  Also, using Marvel Mystery Oil will not negatively affect the anti-slinging or misting charactestics of the motor oil.  While Marvel Mystery Oil does not contain any zinc, the additives in Marvel Mystery Oil do help to reduce metal-to-metal friction and thus wear.