Have you done a compression test yet? If the compression is good then you are most likely drawing oil into the combustion chambers thru the valve guides. That would be corrected by installing new valve seals without removing the cylinder heads. STP will not correct this issue.

If the compression is low and a leakdown test shows worn piston rings then STP and a heavier weight oil will help some but engine rebuilds are the only real fix.

 

Yep, no such thing as Mitch in a can.

 

How much oil does each engine consume?

 

Try some Valvoline VR1 50wt. Texas gets hot

 

I love VR1 for the old flat tappet engines. Has the ZDDP you need.

 

You're correct about my overstatement of the cost - guess I was just being overly dramatic. That said, I did extensive research on the best oil for these old Chevy big block engines and the consensus recommendation was Valvoline 20W-50 VR1 Synthetic Racing Motor Oil.

 

Wonder if that would be to heavy for me in April in Georgian bay . I have not used a drop of oil in 65 hrs using 20 w 40 merc oil. Uts plenty hot now

 

No idea - but there is probably a difference between Texas Hot and Canadian Hot.

 

I think you'd be better off with a non straight weight. You got no use for the 20 part, right? Probably 80 when you wake up. I use to use Mobil 1 15-50 synthetic, but using less oil now with the 20-50 vr1 non syn.