Zzdp

It's zddp.

Decent article on history.

ZDDP: When, Where, What, Why, How? - Engine Builder Magazine

Depends on your motor build, if the car has a catalytic converter and how tight it was built.

Phosphates come into the equation as well.

With no cats, and older engine platforms (even with new rebuilds) many people to go VR1 Racing because of its decent zddp content. Then again - some people swear by synthetics.

Engine builders I trust, who rebuild older platform engines without extreme tight tolerances recommend decent zddp ... so I use it in 4 cars. Newer cars I use Mobil1.