The blends are recommended because of the
zinc. Dave Crower recommends Schaffer's
synthetic blend (tractor
oil) with his lifters, not Mobil 1, because the straight synthetics don't have
zinc.
Kendal was one of the highest rated parafin-based RACING oils until they had to refomulate last year and eliminate the
zinc. If your favorite RACING
oil is available at the auto parts store it won't have zinc for long thanks to government regs.
I don't know what is best myself so I use what my builder recommends. After all, how many National championship winning engines do I build a year.
Scott