This is another deal the Federal Govt. has fucked up thanks to their damn clean air act they pushed through Congress.
Used to be pretty much any oil had "high zinc" in it. Actually the chemical is called ZDDP for short or Zinc Dialkyl Dithio Phosphate. This is necessary to prevent extreme pressure wear.
The EPA demanded it be removed from oil because it slowly poisons catalytic converters over time....more government horseshit!
It makes me wonder how much better this type of oil with "old time" levels of ZDDP would protect our stock engines compared to the catalytic converter friendly oils out there today? Any thoughts?
I did some searching and found this that may be helpful:
http://zddp.net/
http://www.macysgarage.com/myweb6/ZDDP.htm
Hell I remember when Valvoline advertised this miracle chemical as "Chemalloy," Penzoil called it "Z7" and oil was in cans at that time!
HTH
Mike