[Ironangel]

The STP in the blue cans is a good "cheap" source for zinc! I used it (and still do) for years in my 4-stroke Z1 racing motors. It's great stuff for flat tappet motors, the downside of STP oil additive is the "thickening" agent used in it a cellulose paraffin matrix that has tendency to gather or bind together in slack areas such as the top of the heads and corners of the crank case. A racing motor that gets opened up and cleaned regularly it posses no problem. But in daily drivers that run for years of hot and cold running intervals it will collect and cause sludge. Ever pop a valve cover off to find 2" inches of black tar build up around the moving parts? It will clog an oil filter and cause the bypass to open allowing the build up on the heads as well as slack areas in the crank case. Regular oil changes are a must if you use the stuff and before the oil change a can of SeaFoam or Rislone oil additive added to the crank case a few miles before draining the oil helped clean that sludge out...Zinc phosphate (ZDDP) only works when it gets to the moving parts while suspended in the oil...