10-40 havoline with a pint of
over 150,000 miles on my Gto's 421 .. oil changed every 2-2500mi .. over 700 1/4 mile passes (mostly 12.50 bracket) and tons of late night racing ,and lots of road trips .. clean as day one inside .
everything else just gets good grade 20-50 and a touch of marvel ..
(note ; i never use parifin based oil. AE penzoil)