slant 6 oil weight

I'm a little late to this thread. This is my opinion, and others have theirs.
1) Never use a straight grade oil (ie 30 or 40 ),or a non detergent oil, in any auto engine made in the last 60 years.
2)I run "house" brand 10-30 in all my cars, including my race cars. My truck is a 4 cyl, tows my race car, and has 394,*** miles on it with all original engine parts, except for timing chain. I have not had a oil related engine failure in 40 years.
3) I feel syn oils are better then "dyno" oils, but not enough better to justify the cost. Current "dyno" oils are excellent. There are exceptions to using Syn oils, I have one customer that really "beats" on his engine. Heavy loads, highspeed interstate, in drastic temp changes. Him, I recommend syn oil.