slant 6 oil weight

I would just run valvoline VR1 10/30 as long as you have good oil psi at idle at least 10 at 700rpm. It's high on most of the "lists" plenty of zinc for old flat tappet cams, anti foaming additive for hi rpm, thinner oil cools better especially the valve springs, rockers, bearing and drains back to the pan quicker. The new thinking is to run a hi volume or psi pump with thin racing oil like a 0/20 or 5/30. − 0W-5 for the NHRA Pro Stock, 10W-30 for NASCAR .