The Effect of Lubricant Additives on the Durability of Platinum Oxidising Catalysts *

The presence of a metal such as calcium or zinc in a lubricant appears to inhibit the poisoning effect of phosphorus on platinum oxidising catalysts. This is a general conclusion from rig, engine and vehicle tests on lubricants with different additive components. Among the test results reported a lubricant blend with 2.5% by weight ZDDP (0 22% wt Zn) and another blend with 1.25% wt ZDDP plus enough phosphorus containing ashless anti-oxidant to double the phosphorus content of the lubricant both gave satisfactory performance in tersm of catalyst degradation.