well in my 67 dart i have no clue. what ever was in there when i got it. the 68 its 20w50 castrol, the 71 its 10w40 castrol, the 72 its 20w50 valvoline (8 yrs old), the 77 PW is gonna get 10w30 mobil 1 once the engine is rebuilt, the 87 cherokee is runnin 15w50 mobil 1 synthetic with a quart of...