I had a buddy back in the late 60,s and he had a 57 Coupe De ville that smoked a little on start up but settled out quickly and he was bound and determined to to put Castrol Super GTX in it. My dad told him to put 30 wt, non detergent oil. My buddy wasn,t too swift and put in the GTX. The motor threw a quart of oil every couple of miles ater that and he ruined it. Live and learn.