Inliners International Forums General Discussion Engines age old oil question

EOS is Engine Oil Suppliment, the real stuff is sold by GM dealers in the parts department. I've never seen real EOS anywhere else.
I use Valvoline Synpower 20w-50 in the V8 350 [crate motor] in my '71 Jimmy. It seems to run well on the stuff. I broke it in on organic SAE 30 weight. That engine is about 8 years old in a daily runner. I am thinking of going back to organic [regular] 20w-50 due to the fact that $6 a quart is too much for synthetics. I intend to wean it off the synthetic by running Castrol Syntec blend thru one oil change cycle. But lately the Valvoline Synpower has been on sale, so maybe I'll stay synthetic for a while.
In my '68 C/10, I have a 292 L6, that's been operational since Jan '05. I broke it in on non-detergent Napa 30 weight, then switched to detergent Valvoline SAE 30 after the required 500 miles. Since I had a lot of organic Valvoline 20w-50, I ran the 292 on that for maybe a couple of years. On my last oil change I decided to run straight Valvoline SAE 30, for the summer at least. The change in engine tone was noticable. It sounds better, runs better, feels better. Don't know why. But I'm keeping the 30 weight for now.