I now use ZDDP Plus additive to the Pennzoil conventional oil (but ZDDP deprived as mandated) oil I have used for the past 39 years and 178,000 miles in my car. See: http://www.zddplus.com/index.htm

Explore the site in detail. It appears that racing oils may satisfy some ZDDP needs but lack other stuff needed for use in street vehicles.