slant 6 oil weight

dino oil is best to break a motor in, then synthetic. Practically no sludge with synthetic, good stuff.

Oil depends on climate. So.Cal can run straight 30 but why? multiweight is easiest on pump. ITs like this: 10W40 is 10 at startup (thin, perfect to get the oil to the bearings the fastest) and 40 (gooey) at 100C`(212F) or normal operating temperature, nice and thick like older high mileage cars like with their looser bearing tolerances. you can run 0W30 if you want. its still 30W at operating temp. 0W20 is used nowadays to extract the most mileage of new motors. Modern Science at work.