ZDDP is added to Duckhams to enhance lubrication by acting as the ‘anti-wear’ additive. It is important to note that this is different from “extreme pressure” additives, which are found in gear oils (EP oils). They act rather differently so will be covered in more detail elsewhere.
Read full article at ….. https://www.duckhams.com/zddp-what-does-it-all-mean/
So for a selection of recommended classic car engine oils click …… classic car oil